Physical

Physical Physical PhysicsPhysics

The Study of How Matter BehavesThe Study of How Matter Behaves

Physics is the branch of science that concerns Physics is the branch of science that concerns the behavior of matter in our world—the forces the behavior of matter in our world—the forces that cause matter to behave as it does. Physics that cause matter to behave as it does. Physics helps to explain how cellular molecules can helps to explain how cellular molecules can move from a lower concentration in an move from a lower concentration in an organism to a higher one, how ocean tides organism to a higher one, how ocean tides occur, and how matter exists in the states of a occur, and how matter exists in the states of a solid, liquid, or gas. (page 555)solid, liquid, or gas. (page 555)

Physical SciencePhysical SciencePhysicsPhysics


Many of the properties and behaviors of Many of the properties and behaviors of matter can be explained by force and matter can be explained by force and energy. A force shows the presence of energy. A force shows the presence of energy in an environment. Energy is the energy in an environment. Energy is the capacity to do work. The area of physics capacity to do work. The area of physics that deals with forces, energy, and their that deals with forces, energy, and their effect on bodies is mechanics. (page 555)effect on bodies is mechanics. (page 555)


MechanicsMechanics

The study of mechanics was one of the first The study of mechanics was one of the first sciences developed. Ancient Greek philosopher sciences developed. Ancient Greek philosopher and scientist Aristotle theorized that heavy and scientist Aristotle theorized that heavy bodies fall faster than light bodies. This theory bodies fall faster than light bodies. This theory was proved false in the early 17th century by was proved false in the early 17th century by Italian scientist and mathematician Galileo, who Italian scientist and mathematician Galileo, who dropped items of different weights from the dropped items of different weights from the leaning tower of Pisa. (page 556)leaning tower of Pisa. (page 556)


MechanicsMechanics


MechanicsMechanics

The force acting upon the objects was not The force acting upon the objects was not fully understood, however, until fully understood, however, until Englishman Sir Isaac Newton formulated Englishman Sir Isaac Newton formulated laws of gravity and motion that explained laws of gravity and motion that explained how different forces act on objects. (page how different forces act on objects. (page 556)556)


MechanicsMechanics


The Force of GravityThe Force of Gravity

Gravity is the most commonly experienced of all Gravity is the most commonly experienced of all forces in nature. The presence of gravity was first forces in nature. The presence of gravity was first proposed by Newton when he observed the proposed by Newton when he observed the motion of an apple falling from a tree. On the basis motion of an apple falling from a tree. On the basis of this simple observation, he developed the Law of this simple observation, he developed the Law of Universal Gravitation, which holds that every of Universal Gravitation, which holds that every body having a mass exerts an attractive force on body having a mass exerts an attractive force on every other body having a mass in the universe. every other body having a mass in the universe. (page 556)(page 556)



The strength of the force depends on the masses of The strength of the force depends on the masses of the objects and the distance between them. (Mass is the objects and the distance between them. (Mass is the measure of the amount of matter in an object.) the measure of the amount of matter in an object.) Thus, the apple's falling illustrates the gravitational Thus, the apple's falling illustrates the gravitational pull (attraction) of the larger Earth on the smaller pull (attraction) of the larger Earth on the smaller apple. The Law of Universal Gravitation also explains apple. The Law of Universal Gravitation also explains how the planets, attracted by the much larger Sun, how the planets, attracted by the much larger Sun, remain in their orbits as they revolve around it. (page remain in their orbits as they revolve around it. (page 556)556)


NEWTON'S THREE LAWS OF MOTIONNEWTON'S THREE LAWS OF MOTION

The Law of InertiaThe Law of Inertia

A body remains at rest or continues in a state of A body remains at rest or continues in a state of uniform motion unless a force acts on it. For uniform motion unless a force acts on it. For example, when you drive a car and suddenly example, when you drive a car and suddenly jam on the brakes, you continue to move jam on the brakes, you continue to move forward. This is because your body's tendency forward. This is because your body's tendency is to remain in the same state of uniform motion is to remain in the same state of uniform motion (moving forward). The brakes were applied to (moving forward). The brakes were applied to the car, so its uniform motion was changed. the car, so its uniform motion was changed. (page 556)(page 556)



The Law of Applied ForceThe Law of Applied Force

A body's change in speed and direction is A body's change in speed and direction is proportional to the amount of force proportional to the amount of force applied to it. For example, the vanes on a applied to it. For example, the vanes on a windmill, which move by the force of the windmill, which move by the force of the wind, will accelerate according to the wind, will accelerate according to the speed and direction of the wind that drives speed and direction of the wind that drives them. (page 556)them. (page 556)

Physical SciencePhysical Science

PhysicsPhysics


The Law of Action and ReactionThe Law of Action and Reaction

For every action there is an equal but For every action there is an equal but opposite reaction force. For example, a opposite reaction force. For example, a gun's muzzle kicks backward when a gun's muzzle kicks backward when a bullet is discharged from it. (page 556)bullet is discharged from it. (page 556)

Physical SciencePhysical ScienceEXERCISE 1EXERCISE 1

Laws of Force and Motion (page 557)Laws of Force and Motion (page 557)

Directions: Identify the following statements as (G) illustrating Newton'sDirections: Identify the following statements as (G) illustrating Newton's

Law of Universal Gravitation, (I) applying to the Law of Inertia, (AF) Law of Universal Gravitation, (I) applying to the Law of Inertia, (AF) applying to the Law of Applied Force, or (AR) applying to the Law of applying to the Law of Applied Force, or (AR) applying to the Law of Action and Reaction.Action and Reaction.

1. ____ A ball on a pool table rebounds off another ball it just hit.1. ____ A ball on a pool table rebounds off another ball it just hit.

2. ____ A rocket is propelled upward by the powerful downward 2. ____ A rocket is propelled upward by the powerful downward discharge of exhaust gases.discharge of exhaust gases.

3. ____ A bullet fired into the air eventually falls to the ground.3. ____ A bullet fired into the air eventually falls to the ground.

4. ____ A pendulum in a clock, once set in motion, continues to swing, 4. ____ A pendulum in a clock, once set in motion, continues to swing, thereby regulating the clock's movement.thereby regulating the clock's movement.

5. ____ A jet airplane, upon landing, lowers the flaps on its wings. The 5. ____ A jet airplane, upon landing, lowers the flaps on its wings. The flaps create drag, a force that reduces lift and helps the plane to slow flaps create drag, a force that reduces lift and helps the plane to slow down.down.

Physical SciencePhysical ScienceEXERCISE 2 (page 557)EXERCISE 2 (page 557)


Directions: Read the paragraph below and answer the questions that Directions: Read the paragraph below and answer the questions that follow.follow.

An astronaut weighs in before blast-off. He weighs only a fraction of his An astronaut weighs in before blast-off. He weighs only a fraction of his original weight when he steps on a scale on the moon. Journeying to original weight when he steps on a scale on the moon. Journeying to Jupiter, he finds that his weight has increased several times over his original Jupiter, he finds that his weight has increased several times over his original weight.weight.

1. How may these changes in weight be best explained?1. How may these changes in weight be best explained?

(1) the amount of force each planetary body exerts as the astronaut weighs (1) the amount of force each planetary body exerts as the astronaut weighs himselfhimself

(2) the distance from the Sun of the planetary bodies on which he weighs (2) the distance from the Sun of the planetary bodies on which he weighs himselfhimself

(3) changes in the atmospheric pressure on the different heavenly bodies(3) changes in the atmospheric pressure on the different heavenly bodies

(4) the amount of calories consumed during the flight(4) the amount of calories consumed during the flight

(5) the duration of time that elapsed between weigh-ins(5) the duration of time that elapsed between weigh-ins

2. What do you estimate the weight change for the same astronaut would 2. What do you estimate the weight change for the same astronaut would be if he were to land on Mercury?be if he were to land on Mercury?

Physical SciencePhysical ScienceWork, Energy, and PowerWork, Energy, and Power

According to physics, work occurs when a According to physics, work occurs when a force succeeds in moving an object it acts force succeeds in moving an object it acts upon. For example, a person who lifts a upon. For example, a person who lifts a 50-pound weight one foot off the floor is 50-pound weight one foot off the floor is performing work. For work to be performing work. For work to be performed, the movement of the object performed, the movement of the object must be in the same direction as the forcemust be in the same direction as the force—in this case vertical. (page 558)—in this case vertical. (page 558)

Physical SciencePhysical ScienceWork, Energy, and Power (page 558)Work, Energy, and Power (page 558)

Work may be expressed as any force unit Work may be expressed as any force unit times any distance unit and may be written times any distance unit and may be written as follows:as follows:

W = FxDW = FxD

The amount of work done is the amount of The amount of work done is the amount of force multiplied by the distance moved. In force multiplied by the distance moved. In the preceding example, 50 foot-pounds of the preceding example, 50 foot-pounds of work is done when 50 pounds are lifted one work is done when 50 pounds are lifted one foot:foot:

50 lb x 1 ft = 50 ft lb50 lb x 1 ft = 50 ft lb


Work, Energy, and PowerWork, Energy, and Power

Energy is required to do work. In the Energy is required to do work. In the example above, muscular energy is example above, muscular energy is illustrated in the form of a body that is illustrated in the form of a body that is capable of doing work. Energy may be capable of doing work. Energy may be classified as either kinetic or potential classified as either kinetic or potential energy.energy. (page 558)(page 558)



Kinetic energyKinetic energy is energy possessed by a is energy possessed by a body in motion. The form of energy shown body in motion. The form of energy shown by a moving train is kinetic energy.by a moving train is kinetic energy.

(page 558)(page 558)

Physical SciencePhysical ScienceWork, Energy, and PowerWork, Energy, and Power

Potential energyPotential energy is energy that is stored is energy that is stored or is available for use by a body. For or is available for use by a body. For example, coal has potential energy that is example, coal has potential energy that is released only when it is burned. A boulder released only when it is burned. A boulder positioned on a hilltop has potential positioned on a hilltop has potential energy before it is released. When the energy before it is released. When the boulder is pushed, its potential energy boulder is pushed, its potential energy becomes kinetic. (page 558)becomes kinetic. (page 558)



PowerPower is the rate at which work is done. is the rate at which work is done. Power is generally measured in Power is generally measured in horsepower, which is equal to 550 foot-horsepower, which is equal to 550 foot-pounds per second or 33,000 footpounds pounds per second or 33,000 footpounds per minute. (page 558)per minute. (page 558)

Physical SciencePhysical ScienceThe Law of Conservation of EnergyThe Law of Conservation of Energy

The Law of Conservation of Energy holds The Law of Conservation of Energy holds that all of the energy of the universe is that all of the energy of the universe is conserved. The capacity for energy to do conserved. The capacity for energy to do work can be changed from one kind to work can be changed from one kind to another, but it cannot be lost. This another, but it cannot be lost. This principle can be illustrated in the following principle can be illustrated in the following example of energy generated from a example of energy generated from a waterfall. (page 558)waterfall. (page 558)

Physical SciencePhysical ScienceThe Law of Conservation of EnergyThe Law of Conservation of Energy

Water possesses potential energy. When water Water possesses potential energy. When water moves rapidly in a downward motion, drawn by moves rapidly in a downward motion, drawn by the pull of gravity, the potential energy is the pull of gravity, the potential energy is changed into kinetic energy. Kinetic energy changed into kinetic energy. Kinetic energy from a waterfall can be harnessed to power a from a waterfall can be harnessed to power a turbine, a rotary engine, creating rotational turbine, a rotary engine, creating rotational energy. This is sufficient to generate electrical energy. This is sufficient to generate electrical energy, which in turn is converted into light and energy, which in turn is converted into light and heat energy, which we use in our homes. The heat energy, which we use in our homes. The initial potential energy has been changed into initial potential energy has been changed into five different forms. (page 558)five different forms. (page 558)


Forms of Energy (page 559)Forms of Energy (page 559)

Directions: Identify the following statements as Directions: Identify the following statements as either demonstrating kinetic energy (K) or either demonstrating kinetic energy (K) or demonstrating potential energy (P).demonstrating potential energy (P).

1. ____ a strong west wind blowing across a 1. ____ a strong west wind blowing across a region region

2. ____ a stick of unlit dynamite2. ____ a stick of unlit dynamite

3. ____ a hamburger3. ____ a hamburger

4. ____ a waterfall4. ____ a waterfall


Types of Energy (page 559)Types of Energy (page 559)

Directions: Read the following definitions of the five Directions: Read the following definitions of the five types of energy. Then choose the best answers for the types of energy. Then choose the best answers for the questions below.questions below.

nuclear energy - energy from splitting an atom or nuclear energy - energy from splitting an atom or fusing atomsfusing atoms

chemical energy - energy from the reaction of two or chemical energy - energy from the reaction of two or more substances combining with one anothermore substances combining with one another

electrical energy-electrical energy- energy from an electric currentenergy from an electric current

solar energy - energy from the heat of the Sunsolar energy - energy from the heat of the Sun

steam energy - energy from steam pressuresteam energy - energy from steam pressure



1. Which form of energy results from the 1. Which form of energy results from the fission of uranium-235 nuclei that is used to fission of uranium-235 nuclei that is used to generate electrical power?generate electrical power?

(1) nuclear energy(1) nuclear energy

(2) chemical energy(2) chemical energy

(3) electrical energy(3) electrical energy

(4) solar energy(4) solar energy

(5) steam energy(5) steam energy



2. Which form of energy results from the 2. Which form of energy results from the ignition of a gas and air mixture and ignition of a gas and air mixture and powers a car?powers a car?

(1) nuclear energy(1) nuclear energy

(2) chemical energy(2) chemical energy

(3) electrical energy(3) electrical energy

(4) solar energy(4) solar energy

(5) steam energy(5) steam energy


Simple MachinesSimple Machines

A machine is a device that transmits or A machine is a device that transmits or multiplies force. A machine operates on multiplies force. A machine operates on the principle of a little force as being the principle of a little force as being applied through a great distance and a applied through a great distance and a great resistance being overcome through great resistance being overcome through a short distance. (page 560)a short distance. (page 560)



The leverThe lever



A lever is a simple machine used to A lever is a simple machine used to perform work by lifting a great weight. A perform work by lifting a great weight. A

lever is just a bar that is free to pivot on its lever is just a bar that is free to pivot on its support (called a fulcrum). Through the support (called a fulcrum). Through the

use of a lever, for example, a 1,000-pound use of a lever, for example, a 1,000-pound weight can be lifted with relatively little weight can be lifted with relatively little

effort (force). (page 560)effort (force). (page 560)


Simple Machines (page 560)Simple Machines (page 560)

The illustration above shows that it would The illustration above shows that it would take 100 pounds of force for a person to take 100 pounds of force for a person to lift a 1,000-pound weight positioned 1 foot lift a 1,000-pound weight positioned 1 foot from the fulcrum when the lever bar is 10 from the fulcrum when the lever bar is 10 feet long. This may be expressed as feet long. This may be expressed as follows:follows:

1,000 lbx1 ft = 100lbx10ft1,000 lbx1 ft = 100lbx10ft

Physical SciencePhysical ScienceSimple MachinesSimple Machines

In this case a relatively small force (100 In this case a relatively small force (100 lb) applied at a great distance from the lb) applied at a great distance from the object (10 ft) is able to overcome great object (10 ft) is able to overcome great resistance (1,000 lb). According to this resistance (1,000 lb). According to this principle the greater the distance between principle the greater the distance between the fulcrum and the applied force, the less the fulcrum and the applied force, the less force required to perform the work. (page force required to perform the work. (page 560)560)

Physical SciencePhysical ScienceSimple MachinesSimple Machines

The wheelbarrow, The wheelbarrow, the crowbar, the the crowbar, the pulley, and the pulley, and the inclined plane are inclined plane are simple machines. simple machines. Complex machines Complex machines are made up of more are made up of more than one simple than one simple machine. (page 560)machine. (page 560)



Directions: Choose the best answer for Directions: Choose the best answer for each of the following questions.each of the following questions.

1. According to the principle that a little 1. According to the principle that a little force applied through a great distance can force applied through a great distance can overcome great resistance, which would be overcome great resistance, which would be most likely to happen if the lever bar in the most likely to happen if the lever bar in the preceding illustration is increased to 20 feet preceding illustration is increased to 20 feet in length and the weight remained at the end in length and the weight remained at the end of the bar?of the bar?



(1) The effort to lift the weight would increase to (1) The effort to lift the weight would increase to 150 pounds of applied force.150 pounds of applied force.

(2) The effort to lift the weight would remain at (2) The effort to lift the weight would remain at 100 pounds of applied force.100 pounds of applied force.

(3) The effort would be decreased by half, to 50 (3) The effort would be decreased by half, to 50 pounds of applied force.pounds of applied force.

(4) The resistance of the weight would double.(4) The resistance of the weight would double.

(5) The resistance of the weight would triple.(5) The resistance of the weight would triple.


EXERCISE 5EXERCISE 5


2. What are some other types of 2. What are some other types of household items that could be considered household items that could be considered levers? (Hint: Any tool that makes the job levers? (Hint: Any tool that makes the job easier is likely a lever.)easier is likely a lever.)


The Nature of Heat and EnergyThe Nature of Heat and Energy

Today we know that heat is the result of Today we know that heat is the result of the random motion of molecules. It is the random motion of molecules. It is nothing more than energy itself. One nothing more than energy itself. One theory of physics that has contributed theory of physics that has contributed greatly to our understanding of the greatly to our understanding of the phenomenon of heat is kinetic theory, a phenomenon of heat is kinetic theory, a basic theory that explains how different basic theory that explains how different states of matter can exist. (page 561)states of matter can exist. (page 561)

Physical SciencePhysical ScienceThe Nature of Heat and EnergyThe Nature of Heat and Energy

The Kinetic Theory of MatterThe Kinetic Theory of Matter

According to the Kinetic Theory of Matter, According to the Kinetic Theory of Matter, matter exists in three states— solid, liquid, matter exists in three states— solid, liquid, or gas. A fourth state, or gas. A fourth state, plasmaplasma, is an , is an ionized gas; the Sun is made up of ionized gas; the Sun is made up of plasma. The form, or phase, of matter is plasma. The form, or phase, of matter is determined by the motion of the determined by the motion of the molecules within it.molecules within it. (page 561)(page 561)



SolidsSolids are composed of atoms or are composed of atoms or molecules in limited motion. These atoms molecules in limited motion. These atoms or molecules are in direct contact with one or molecules are in direct contact with one another, allowing little or no space for another, allowing little or no space for random movement. The attractive forces random movement. The attractive forces of the particles keep the solid intact and of the particles keep the solid intact and give the solid its definite shape and give the solid its definite shape and structure. (page 561)structure. (page 561)




In In liquidsliquids, individual atoms or molecules , individual atoms or molecules are able to move past one another into are able to move past one another into new positions, giving this form of matter new positions, giving this form of matter its fluidity. Cohesive forces hold liquids its fluidity. Cohesive forces hold liquids intact. (page 561)intact. (page 561)



GasesGases are substances in which the are substances in which the individual atoms or molecules are in individual atoms or molecules are in constant random motion. The motion, or constant random motion. The motion, or kinetic energy, increases along with an kinetic energy, increases along with an increase in temperature. Molecules are increase in temperature. Molecules are unable to hold together, and this property unable to hold together, and this property gives gases the ability to flow or spread out gives gases the ability to flow or spread out to fill the container in which they are placed. to fill the container in which they are placed. (page 562)(page 562)



Heat, Temperature, and the States of Heat, Temperature, and the States of MatterMatter

The state of matter depends on its heat The state of matter depends on its heat content. Temperature is a measure of heat content. Temperature is a measure of heat intensity. The change from one state of intensity. The change from one state of matter to another involves the addition or matter to another involves the addition or subtraction of a certain amount of heat subtraction of a certain amount of heat per gram of substance. (page 562)per gram of substance. (page 562)


Heat, Temperature, and the States of MatterHeat, Temperature, and the States of Matter

For example, at 32 degrees Fahrenheit, For example, at 32 degrees Fahrenheit, water, a liquid, changes to ice, a solid. When water, a liquid, changes to ice, a solid. When the temperature is raised above 32 degrees the temperature is raised above 32 degrees Fahrenheit, the ice, a solid, changes to Fahrenheit, the ice, a solid, changes to water, a liquid. At temperatures at or above water, a liquid. At temperatures at or above 212 degrees Fahrenheit, the boiling point of 212 degrees Fahrenheit, the boiling point of water, the water changes to steam, a water, the water changes to steam, a gaseous state. Impurities in water affect its gaseous state. Impurities in water affect its freezing point. (page 562)freezing point. (page 562)




Certain materials expand when their Certain materials expand when their temperatures are raised and shrink when temperatures are raised and shrink when they are lowered. Liquids expand more they are lowered. Liquids expand more noticeably than solids, but gases expand noticeably than solids, but gases expand even more. The mercury thermometer even more. The mercury thermometer employs this principle. Temperature can be employs this principle. Temperature can be measured in degrees centigrade or degrees measured in degrees centigrade or degrees Fahrenheit. (page 562)Fahrenheit. (page 562)



On the centigrade (or Celsius) scale, 0 On the centigrade (or Celsius) scale, 0 degrees represents the freezing point of degrees represents the freezing point of water, and 100 degrees is the boiling water, and 100 degrees is the boiling point. On the Fahrenheit scale, 32 point. On the Fahrenheit scale, 32 degrees represents the freezing point of degrees represents the freezing point of water, and 212 degrees is the boiling water, and 212 degrees is the boiling point. (page 562)point. (page 562)




Temperature is measured in degrees by Temperature is measured in degrees by thermometer, and heat is measured by the thermometer, and heat is measured by the calorie or British Thermal Unit (BTU). A calorie or British Thermal Unit (BTU). A calorie is the amount of heat needed to raise calorie is the amount of heat needed to raise one gram of water one degree centigrade. one gram of water one degree centigrade. The BTU is the amount of heat required to The BTU is the amount of heat required to raise one pound of water 1 degree raise one pound of water 1 degree Fahrenheit. (page 562)Fahrenheit. (page 562)



Heat is transferred by three methods. The Heat is transferred by three methods. The first is called conduction, the transfer of first is called conduction, the transfer of heat between objects that are in direct heat between objects that are in direct contact. You have experienced this contact. You have experienced this whenever you have picked up a hot item, whenever you have picked up a hot item, such as a handle on a heated pan. The such as a handle on a heated pan. The second method is convection. (page 562)second method is convection. (page 562)




This method depends on the currents of This method depends on the currents of water and air. When you are adding hot water and air. When you are adding hot water to one end of the bathtub filled with water to one end of the bathtub filled with water, convection transfers the heat to the water, convection transfers the heat to the rest of the water. The third method is rest of the water. The third method is radiation. You can feel waves of heat by radiation. You can feel waves of heat by putting your hands near a radiator (used to putting your hands near a radiator (used to heat many apartments). (page 562)heat many apartments). (page 562)


Kinetic Theory of Matter (page 563)Kinetic Theory of Matter (page 563)

Directions: Identify the following statements as either Directions: Identify the following statements as either true (T) or false (F). 1. ___ There is more rigid true (T) or false (F). 1. ___ There is more rigid molecular structure in a solid than in a gas.molecular structure in a solid than in a gas.

2. ___ An increase in temperature decreases the 2. ___ An increase in temperature decreases the molecular motion of a gas.molecular motion of a gas.

3. ___ Molecules moving past each other in a liquid 3. ___ Molecules moving past each other in a liquid give it fluidity.give it fluidity.

4. ___ Molecules in a gas are close together and 4. ___ Molecules in a gas are close together and exhibit little motion. exhibit little motion.

5. ___ Heat is transferred by conduction, convection, 5. ___ Heat is transferred by conduction, convection, or coercion.or coercion.


Heat and TemperatureHeat and Temperature

Directions: Read the passage below and Directions: Read the passage below and answer the questions that follow.answer the questions that follow.

Different materials expand at different Different materials expand at different degrees of temperature change and in degrees of temperature change and in different percentages of their length, different percentages of their length, volume, or surface. (page 564)volume, or surface. (page 564)



Buckling can occur when a material such as Buckling can occur when a material such as asphalt used for road surfaces reacts to asphalt used for road surfaces reacts to changes in temperature, causing potholes. changes in temperature, causing potholes. This is one of the reasons for the This is one of the reasons for the widespread use of reinforced concrete widespread use of reinforced concrete (concrete with a steel framework) rather than (concrete with a steel framework) rather than asphalt on road surfaces and the use of asphalt on road surfaces and the use of reinforced concrete in high-rise apartment reinforced concrete in high-rise apartment construction. (page 564)construction. (page 564)


Heat and Temperature (page 564)Heat and Temperature (page 564)

1. What does the widespread use of reinforced concrete in 1. What does the widespread use of reinforced concrete in construction suggest?construction suggest?

(1) Concrete and steel expand and contract at nearly the (1) Concrete and steel expand and contract at nearly the same temperatures.same temperatures.

(2) Reinforced concrete expands at temperatures much (2) Reinforced concrete expands at temperatures much higher than ordinary asphalt and does not buckle.higher than ordinary asphalt and does not buckle.

(3) Reinforced concrete does not expand and contract at all.(3) Reinforced concrete does not expand and contract at all.

(4) Asphalt can be used only on roadways and never in (4) Asphalt can be used only on roadways and never in construction.construction.

(5) Asphalt is much more expensive and harder to use than (5) Asphalt is much more expensive and harder to use than concrete.concrete.


Heat and Temperature (page 564)Heat and Temperature (page 564)

2. Which heat transfer method is 2. Which heat transfer method is demonstrated when your hand is positioned demonstrated when your hand is positioned directly over the flame of a lighted candle?directly over the flame of a lighted candle?

(1) convection(1) convection

(2) conduction(2) conduction

(3) radiation(3) radiation

(4) expansion(4) expansion

(5) coersion(5) coersion

Physical SciencePhysical ScienceThe Nature of WavesThe Nature of Waves

A wave is a periodic or harmonic A wave is a periodic or harmonic disturbance in space or through a medium disturbance in space or through a medium (water, for instance) by which energy is (water, for instance) by which energy is transmitted. Water, sound, and light all transmitted. Water, sound, and light all travel in waves. The illumination a lamp travel in waves. The illumination a lamp provides comes from light waves (a form provides comes from light waves (a form of electromagnetic waves) while the music of electromagnetic waves) while the music emanating from a stereo comes from emanating from a stereo comes from sound waves. (page 565)sound waves. (page 565)


WaveWave


The Nature of WavesThe Nature of Waves

The powers to preserve food and warm it The powers to preserve food and warm it come from electromagnetic waves, and come from electromagnetic waves, and the power that transmits signals to a the power that transmits signals to a television set comes from radio waves television set comes from radio waves (another form of electromagnetic waves). (another form of electromagnetic waves). The energy that gives a waterbed its The energy that gives a waterbed its soothing motion comes from water waves. soothing motion comes from water waves. (page 565)(page 565)


Types and Properties of WavesTypes and Properties of Waves

Waves transmit energy in different ways, Waves transmit energy in different ways, and all phases of matter transmit waves. and all phases of matter transmit waves. An example of a solid transmitting wave An example of a solid transmitting wave energy is an earthquake that takes place energy is an earthquake that takes place when rocks are under pressure and snap when rocks are under pressure and snap or slide into new positions. Waves that are or slide into new positions. Waves that are felt and seen in water are examples of a felt and seen in water are examples of a liquid transmitting wave energy. (page 565)liquid transmitting wave energy. (page 565)




Gases also transmit wave energy, as in an Gases also transmit wave energy, as in an explosion, when heat, sound, and light explosion, when heat, sound, and light waves are generated. Two basic types of waves are generated. Two basic types of waves exist: longitudinal waves and waves exist: longitudinal waves and transverse waves. (page 565)transverse waves. (page 565)




Longitudinal waveLongitudinal wave

Particles of the medium move back and Particles of the medium move back and forth in the same direction as the wave forth in the same direction as the wave itself moves. An example of a longitudinal itself moves. An example of a longitudinal wave is a sound wave that occurs when a wave is a sound wave that occurs when a tuning fork is tapped, as shown below. tuning fork is tapped, as shown below. (page 565)(page 565)


Types and Properties of Types and Properties of Waves (page 565)Waves (page 565)

LONGITUDINAL WAVELONGITUDINAL WAVE

When a tuning fork is When a tuning fork is tapped, the prongs move tapped, the prongs move from right to left in a rapid from right to left in a rapid periodic motion. A sound periodic motion. A sound wave is produced, and it wave is produced, and it moves parallel (right and moves parallel (right and left) to the moving prong.left) to the moving prong.


Types and Properties of Waves (page Types and Properties of Waves (page 565)565)

Transverse waveTransverse wave

Particles of the medium move at right Particles of the medium move at right angles to the direction of the wave's angles to the direction of the wave's movement. An example of a transverse movement. An example of a transverse wave is one that occurs when a pebble is wave is one that occurs when a pebble is tossed into a still pond. Light travels in tossed into a still pond. Light travels in transverse waves. (Page 565)transverse waves. (Page 565)


Types and Properties of Types and Properties of Waves (page 565)Waves (page 565)

TRANSVERSE WAVETRANSVERSE WAVE

When a stone is dropped When a stone is dropped into a pond, the waves into a pond, the waves produced appear to produced appear to move outward. These move outward. These waves move at right waves move at right angles to the dropped angles to the dropped stone. (page 565)stone. (page 565)



Waves have two components, a crest and Waves have two components, a crest and a trough. A crest is the point of highest a trough. A crest is the point of highest displacement in a wave, and the trough is displacement in a wave, and the trough is the point of lowest displacement. Crests the point of lowest displacement. Crests and troughs are easily visible in water and troughs are easily visible in water waves. (page 566)waves. (page 566)


Two specific characteristics of a wave are Two specific characteristics of a wave are length and frequency:length and frequency:

• • Wavelength is defined as the distance Wavelength is defined as the distance between two successive wave crests or between two successive wave crests or two successive wave troughs.two successive wave troughs.

• • Wave frequency is the number of wave Wave frequency is the number of wave crests that pass a given point per second. crests that pass a given point per second. (page 566)(page 566)


Therefore, the shorter the wavelength, the Therefore, the shorter the wavelength, the higher the wave frequency. In fact, a wave's higher the wave frequency. In fact, a wave's speed equals the wavelength times the wave speed equals the wavelength times the wave frequency.frequency.

When a source of a wave is in motion, a When a source of a wave is in motion, a compression of the wavelength is detected. compression of the wavelength is detected. This can be demonstrated with sound waves. This can be demonstrated with sound waves. As a train passes you by while you are standing As a train passes you by while you are standing on the platform, you will notice a distinct drop in on the platform, you will notice a distinct drop in the pitch or sound quality. (page 566)the pitch or sound quality. (page 566)


This drop in sound pitch is heard by the This drop in sound pitch is heard by the observers standing on the side during an observers standing on the side during an automotive race such as the Indianapolis 500. automotive race such as the Indianapolis 500. Water waves demonstrate the same Water waves demonstrate the same compression in the direction of motion. The compression in the direction of motion. The water waves in the front of a boat are squeezed water waves in the front of a boat are squeezed together, while those at the rear of the boat are together, while those at the rear of the boat are far apart. This is referred to as the Doppler far apart. This is referred to as the Doppler Effect. Scientists use the Doppler Effect to Effect. Scientists use the Doppler Effect to forecast tornadoes and to detect the motions of forecast tornadoes and to detect the motions of stars in our galaxy. (page 566)stars in our galaxy. (page 566)



Sound waves, as illustrated above, are Sound waves, as illustrated above, are longitudinal waves. A musical pitch, or tone, is longitudinal waves. A musical pitch, or tone, is heard when there is a definite frequency to a heard when there is a definite frequency to a wave. The lower the frequency, the lower the wave. The lower the frequency, the lower the tone. For example, the frequency of a bass tone. For example, the frequency of a bass speaker in a stereo system is lower than a speaker in a stereo system is lower than a tweeter, or high-frequency speaker, because tweeter, or high-frequency speaker, because the low-pitched sound of the bass results from the low-pitched sound of the bass results from a lower number of vibrations per second. (page a lower number of vibrations per second. (page 566)566)


A sound wave is a wave of compression. A sound wave is a wave of compression. It begins at a source—in the case above, It begins at a source—in the case above, a horn speaker. The speaker vibrates, a horn speaker. The speaker vibrates, compressing the air in front of it and, like compressing the air in front of it and, like a spring, pushes it away. As the wave a spring, pushes it away. As the wave passes, the air molecules are forced passes, the air molecules are forced together. The sensation of hearing results together. The sensation of hearing results when these waves strike the eardrum. when these waves strike the eardrum. (page 566)(page 566)



Sound waves can travel through solids, Sound waves can travel through solids, liquids, and gases. In fact, the human liquids, and gases. In fact, the human body can be a medium for sound waves. body can be a medium for sound waves. Ultrasonic waves, very high-pitched Ultrasonic waves, very high-pitched waves, are used in medicine today to waves, are used in medicine today to detect diseases or to show images of detect diseases or to show images of unborn fetuses. (page 566)unborn fetuses. (page 566)


Wave TypesWave Types

Directions: In the space provided, write L if the Directions: In the space provided, write L if the example is an example of a longitudinal wave and T if example is an example of a longitudinal wave and T if it is an example of a transverse wave.it is an example of a transverse wave.

1. ____ a wave that can be seen when a loose rope 1. ____ a wave that can be seen when a loose rope held end to end is jerked at one endheld end to end is jerked at one end

2. ____ the noise caused by the detonation of an 2. ____ the noise caused by the detonation of an atomic bomb atomic bomb

3. ____ the hum created when an arrow is released 3. ____ the hum created when an arrow is released from a bowfrom a bow

4. ____ waves that appear on the surface of the 4. ____ waves that appear on the surface of the oceanocean


Properties of Waves (page 567)Properties of Waves (page 567)

Directions: Look at the illustration below Directions: Look at the illustration below and choose the best answers to the and choose the best answers to the questions that follow.questions that follow.



1. According to the illustration above, which 1. According to the illustration above, which points could be used to measure points could be used to measure wavelength?wavelength?

(1) T and Y(1) T and Y

(2) X and Y(2) X and Y

(3) Z and Y(3) Z and Y

(4) V and W(4) V and W

(5) T, X, and U(5) T, X, and U



2. The Doppler Effect is used for which 2. The Doppler Effect is used for which of the following purposes?of the following purposes?

(1) to find fish in lakes(1) to find fish in lakes

(2) to predict storms and tornadoes(2) to predict storms and tornadoes

(3) to test wave frequency(3) to test wave frequency

(4) to reflect images to satellites(4) to reflect images to satellites

(5) to heighten sound in stereos(5) to heighten sound in stereos

Physical SciencePhysical ScienceThe Nature of LightThe Nature of Light

Physicists define light as a form of Physicists define light as a form of electromagnetic energy that stimulates electromagnetic energy that stimulates sensitive cells of the retina of the human sensitive cells of the retina of the human eye to cause perception of vision. eye to cause perception of vision. Electromagnetic energy can be expressed Electromagnetic energy can be expressed in wavelength ranges along a continuum, in wavelength ranges along a continuum, or spectrum. Light occupies the center of a or spectrum. Light occupies the center of a spectrum that ranges from the low end spectrum that ranges from the low end (gamma rays) to the high end (radio (gamma rays) to the high end (radio waves). (page 568)waves). (page 568)


Electromagnetic SpectrumElectromagnetic Spectrum


The other rays that occupy the The other rays that occupy the electromagnetic spectrum are Xrays, electromagnetic spectrum are Xrays, ultraviolet rays, and infrared rays. ultraviolet rays, and infrared rays. Ultraviolet rays are invisible and are Ultraviolet rays are invisible and are chiefly responsible for sunburn and tan. chiefly responsible for sunburn and tan. Heat-emitting objects such as the sun or a Heat-emitting objects such as the sun or a radiator send out infrared rays that can be radiator send out infrared rays that can be detected only by certain sensitive detected only by certain sensitive instruments. (page 568)instruments. (page 568)


Electromagnetic SpectrumElectromagnetic Spectrum


The visible rays of the spectrum are The visible rays of the spectrum are recognized by the human eye as color. In recognized by the human eye as color. In order, these colors are red, orange, order, these colors are red, orange, yellow, green, blue, indigo (deep blue), yellow, green, blue, indigo (deep blue), and violet. The shortest wavelengths that and violet. The shortest wavelengths that we can see are those we call violet; the we can see are those we call violet; the longest ones are those we call red. (page longest ones are those we call red. (page 568)568)


Two theories about the nature of light Two theories about the nature of light exist: the wave theory and the particle exist: the wave theory and the particle theory. These theories seem to oppose theory. These theories seem to oppose each other but really just focus on each other but really just focus on different properties of light. According to different properties of light. According to the Wave Theory of Light, light is a the Wave Theory of Light, light is a luminous energy emitted by a light source luminous energy emitted by a light source and travels through space as a transverse and travels through space as a transverse wave. (page 568)wave. (page 568)


The Nature of LightThe Nature of Light

According to the Particle Theory of Light, According to the Particle Theory of Light, light energy is both radiated (transmitted) light energy is both radiated (transmitted) and absorbed as tiny packets, or bundles, and absorbed as tiny packets, or bundles, and not as continuous waves. Atoms and and not as continuous waves. Atoms and molecules are able to emit or absorb light molecules are able to emit or absorb light energy in specific amounts. (page 568)energy in specific amounts. (page 568)


The Photoelectric PrincipleThe Photoelectric Principle

Directions: Read the passage below and Directions: Read the passage below and answer the question that follows.answer the question that follows.

The electric eye, or photoelectric cell, is a The electric eye, or photoelectric cell, is a mechanism used to open and close a mechanism used to open and close a garage door when a beam of light is garage door when a beam of light is activated or broken. The principle of the activated or broken. The principle of the electric eye is based on the photoelectric electric eye is based on the photoelectric effect. (page 569)effect. (page 569)



The photoelectric effect occurs when a The photoelectric effect occurs when a beam of light strikes certain metals, beam of light strikes certain metals, causing electrons to be knocked out of the causing electrons to be knocked out of the metal, producing an electric current. This metal, producing an electric current. This is how it happens: (page 569)is how it happens: (page 569)



Light falling on the inside of a bulb coated Light falling on the inside of a bulb coated with an active substance causes electrons to with an active substance causes electrons to be emitted. The electrons are attracted to a be emitted. The electrons are attracted to a positively charged electrode positioned in positively charged electrode positioned in the center of the bulb as a filament. An the center of the bulb as a filament. An electric current results when the electrons electric current results when the electrons (negatively charged particles) are attracted (negatively charged particles) are attracted to the positively charged particles of the to the positively charged particles of the electrode. (page 569)electrode. (page 569)



It is observed that electrons are knocked loose It is observed that electrons are knocked loose only when a certain light energy is reached. only when a certain light energy is reached. The current can then be controlled by changes The current can then be controlled by changes in light intensity. It appears that electrons are in light intensity. It appears that electrons are able to absorb only a certain amount of light at able to absorb only a certain amount of light at one time. When light shines on the electric eye, one time. When light shines on the electric eye, a current is established and the door moves. a current is established and the door moves. When the beam of light is broken, the door When the beam of light is broken, the door stops. (page 569)stops. (page 569)


The Photoelectric Principle (page 569)The Photoelectric Principle (page 569)

How does the principle of the electric eye act?How does the principle of the electric eye act?

(1) to support the wave theory of light that light comes only (1) to support the wave theory of light that light comes only from a luminous sourcefrom a luminous source

(2) to dispute the belief that all light exists only as a (2) to dispute the belief that all light exists only as a continuous wavecontinuous wave

(3) to support the particle theory of light, which states that (3) to support the particle theory of light, which states that light energy is transmitted in packets and bundles and not light energy is transmitted in packets and bundles and not as wavesas waves

(4) to complement the idea that light acts like particles in a (4) to complement the idea that light acts like particles in a wavewave

(5) to contradict the idea that light is generated only in a star(5) to contradict the idea that light is generated only in a star


PROPERTIES OF LIGHT WAVES (page 570)PROPERTIES OF LIGHT WAVES (page 570)

Reflection -Reflection -the angular return of a light wave the angular return of a light wave that occurs when it strikes a shiny surfacethat occurs when it strikes a shiny surface

Example: light bouncing off a mirrorExample: light bouncing off a mirror

Refraction - Refraction - the apparent bending of light the apparent bending of light waves as they pass from one medium to waves as they pass from one medium to anotheranother

Example: drinking straw looking broken in a Example: drinking straw looking broken in a glass of waterglass of water

Physical SciencePhysical SciencePROPERTIES OF LIGHT WAVES (page PROPERTIES OF LIGHT WAVES (page

570)570)

Diffraction - Diffraction - the bending of light waves the bending of light waves according to their wavelengths as they according to their wavelengths as they pass near the edge of an obstacle or pass near the edge of an obstacle or through a small openingthrough a small opening

Example: "rainbow" pattern on an old Example: "rainbow" pattern on an old phonograph record held edgewise toward phonograph record held edgewise toward white lightwhite light


570)570)

Interference - Interference - the altering of the altering of brightness of light rays that occurs when brightness of light rays that occurs when they interfere with each other, causing they interfere with each other, causing reinforcement and cancellationreinforcement and cancellation

Example: holding thumb and finger Example: holding thumb and finger together and looking through the opening together and looking through the opening at a bright lightat a bright light


570)570)

PolarizationPolarization - the restriction of light - the restriction of light waves to a particular plane, horizontal or waves to a particular plane, horizontal or vertical vertical

Example: sunglasses that minimize glare Example: sunglasses that minimize glare off shiny surfacesoff shiny surfaces


Properties of Light Waves (page 570)Properties of Light Waves (page 570)

Directions: Use the information above to choose the best Directions: Use the information above to choose the best answer for each question below.answer for each question below.

1. A coin lying at the bottom of a pool is located at a 1. A coin lying at the bottom of a pool is located at a different point from where the eye perceives it to be. The different point from where the eye perceives it to be. The light rays from the coin bend as they pass from water to light rays from the coin bend as they pass from water to air. This demonstratesair. This demonstrates

(1)(1) reflectionreflection

(2)(2) refractionrefraction

(3)(3) diffractiondiffraction

(4)(4) interferenceinterference

(5)(5) polarizationpolarization


Properties of Light Waves (page 570)Properties of Light Waves (page 570)

2. Rays of light striking a polished piece of 2. Rays of light striking a polished piece of chrome appear to bounce off its surface. chrome appear to bounce off its surface. This demonstratesThis demonstrates

(1)(1) reflectionreflection

(2)(2) refractionrefraction

(3)(3) diffractiondiffraction

(4)(4) interferenceinterference

(5)(5) polarizationpolarization

Physical SciencePhysical ScienceThe Nature of ElectricityThe Nature of Electricity

Electricity is another invisible but vital Electricity is another invisible but vital form of energy that we often take for form of energy that we often take for granted. Without electricity, however, our granted. Without electricity, however, our lives would be paralyzed. The more lives would be paralyzed. The more urbanized we become, the more urbanized we become, the more dependent on electricity we are. Nuclear dependent on electricity we are. Nuclear energy, despite its potential hazards, is an energy, despite its potential hazards, is an important source for generating the important source for generating the electrical power we need. (page 571)electrical power we need. (page 571)


The Nature of ElectricityThe Nature of Electricity

Physicists define electricity as a form of Physicists define electricity as a form of energy that results from the flow of loose energy that results from the flow of loose electrons— electrons weakly bound to electrons— electrons weakly bound to atoms. Electricity is closely related to atoms. Electricity is closely related to magnetism; therefore, the attractive force magnetism; therefore, the attractive force of magnetism must be discussed in order of magnetism must be discussed in order to explain electrical energy. (page 571)to explain electrical energy. (page 571)


Magnetism and Electrical ChargesMagnetism and Electrical Charges

The points of attraction at opposite ends of a The points of attraction at opposite ends of a magnet are called its poles. Magnets have a magnet are called its poles. Magnets have a north and a south pole, also called a positive north and a south pole, also called a positive and a negative pole. The opposite poles of and a negative pole. The opposite poles of two magnets (a north pole and a south pole) two magnets (a north pole and a south pole) will attract each other. Correspondingly, will attract each other. Correspondingly, similar poles (two north or south poles) will similar poles (two north or south poles) will repel each other. (page 571)repel each other. (page 571)




The space around magnets is called a The space around magnets is called a magnetic field. Only a few natural and magnetic field. Only a few natural and synthetic materials can be magnetized—synthetic materials can be magnetized—iron, steel, nickel, cobalt, and some alloys. iron, steel, nickel, cobalt, and some alloys. A magnet, with its poles and lines of force, A magnet, with its poles and lines of force, is illustrated below. (page 571)is illustrated below. (page 571)


Magnetic Lines of ForceMagnetic Lines of Force

Every magnetic substance contains Every magnetic substance contains domains, groups of molecules with attractive domains, groups of molecules with attractive forces. Before a substance is magnetized, forces. Before a substance is magnetized, these domains are arranged randomly so these domains are arranged randomly so that the field of one domain is canceled out that the field of one domain is canceled out by the field of another. When the substance by the field of another. When the substance is magnetized, the domains line up parallel is magnetized, the domains line up parallel to the lines of force, with all north poles to the lines of force, with all north poles facing in the same direction. (page 571)facing in the same direction. (page 571)



This arrangement makes a permanent This arrangement makes a permanent magnet out of a material in which the magnet out of a material in which the domains are too weak to disarrange domains are too weak to disarrange themselves.themselves.

In most elements the atoms possess a In most elements the atoms possess a slight magnetic field because of their slight magnetic field because of their spinning electrons. (page 571)spinning electrons. (page 571)



However, the fields cancel each other out However, the fields cancel each other out because the atoms rotate and spin in because the atoms rotate and spin in different directions. In a magnet, however, different directions. In a magnet, however, whole groups of atoms line up in one whole groups of atoms line up in one direction and increase one another's direction and increase one another's magnetic effect rather than cancel it out. magnetic effect rather than cancel it out. These magnetic concentrations are These magnetic concentrations are magnetic domains. (page 571)magnetic domains. (page 571)


Static Electricity and MagnetismStatic Electricity and Magnetism

Static electricity is a stationary electrical Static electricity is a stationary electrical charge caused by the friction of two charge caused by the friction of two objects, one positively charged and the objects, one positively charged and the other negatively charged. Static electricity other negatively charged. Static electricity operates on the same principle as operates on the same principle as magnetism. The rubbing of the carpet by magnetism. The rubbing of the carpet by your shoes causes your body to become your shoes causes your body to become electrified. (page 572)electrified. (page 572)



The shock you feel is caused by your The shock you feel is caused by your negatively charged body being neutralized negatively charged body being neutralized by the positive charge of the object you by the positive charge of the object you touch. Upon contact your body is no longer touch. Upon contact your body is no longer charged. Static electricity is stored and does charged. Static electricity is stored and does not move. The charged object must be not move. The charged object must be brought into contact with another object that brought into contact with another object that has an opposite charge for electrical shock has an opposite charge for electrical shock to occur. (page 572)to occur. (page 572)


EXERCISE 12EXERCISE 12

GED PRACTICEGED PRACTICE

Electricity and MagnetismElectricity and Magnetism

Directions: Choose the best answer for Directions: Choose the best answer for the questions on page 573, The first the questions on page 573, The first question is based on the following question is based on the following paragraph. paragraph.


Electricity and MagnetismElectricity and Magnetism

Earth itself is surrounded by a magnetic Earth itself is surrounded by a magnetic field. This may be because of strong electric field. This may be because of strong electric currents in Earth's core and the rotation of currents in Earth's core and the rotation of Earth. The north magnetic pole is located in Earth. The north magnetic pole is located in Canada; the south magnetic pole is in nearly Canada; the south magnetic pole is in nearly the opposite location. The strong magnetic the opposite location. The strong magnetic attraction of these poles tends to align the attraction of these poles tends to align the needle of a compass in a northerly-southerly needle of a compass in a northerly-southerly direction. (page 572)direction. (page 572)


Electricity and Magnetism (page 573)Electricity and Magnetism (page 573)

1. What makes a compass tell direction?1. What makes a compass tell direction?

(1) The whole Earth acts as a magnet.(1) The whole Earth acts as a magnet.

(2) The Chinese discovered the magnetic (2) The Chinese discovered the magnetic poles.poles.

(3) The Greeks discovered the magnetic poles.(3) The Greeks discovered the magnetic poles.

(4) Large iron deposits are located in Canada.(4) Large iron deposits are located in Canada.

(5) The magnetic attraction of Earth is (5) The magnetic attraction of Earth is increasing.increasing.


Electricity and Magnetism (page 573)Electricity and Magnetism (page 573)

2. Which of the following would be 2. Which of the following would be attracted to either pole of a magnet?attracted to either pole of a magnet?

(1) a piece of aluminum(1) a piece of aluminum

(2) a piece of brass(2) a piece of brass

(3) a piece of tin(3) a piece of tin

(4) an unmagnetized piece of cobalt(4) an unmagnetized piece of cobalt

(5) a magnetized piece of cobalt(5) a magnetized piece of cobalt

Physical SciencePhysical ScienceElectric CurrentsElectric Currents

Early scientists who experimented with Early scientists who experimented with electric charges found that charges could electric charges found that charges could move easily through certain materials called move easily through certain materials called conductors. As you learned in the chemistry conductors. As you learned in the chemistry section, metal was found to be a good section, metal was found to be a good conductor of electricity, as were salt conductor of electricity, as were salt solutions, acids, and hot gases. Other solutions, acids, and hot gases. Other materials such as rubber were found not to materials such as rubber were found not to conduct charges at all. These materials are conduct charges at all. These materials are called insulators. (page 573)called insulators. (page 573)

Physical SciencePhysical ScienceElectric CurrentsElectric Currents

An electric current is created by an electric An electric current is created by an electric charge in motion. In a solid conductor, such charge in motion. In a solid conductor, such as wire, the current is a stream of moving as wire, the current is a stream of moving electrons. In a liquid or gas, the current may electrons. In a liquid or gas, the current may be positively and negatively charged atomsbe positively and negatively charged atoms— ions. An electric current flowing through a — ions. An electric current flowing through a solid conductor can be compared to the flow solid conductor can be compared to the flow of water through the pipes in your plumbing of water through the pipes in your plumbing system. (page 573)system. (page 573)


Electric CurrentsElectric Currents

An electric current moves slowly—about a An electric current moves slowly—about a hundredth of an inch per second. hundredth of an inch per second. Although our lights come on instantly Although our lights come on instantly when a switch is turned on, it is because when a switch is turned on, it is because the wires are always filled with electrons, the wires are always filled with electrons, just as a water pipe is always filled with just as a water pipe is always filled with water. (page 573)water. (page 573)


ElectromagnetsElectromagnets

An electromagnet is a core of soft magnetic An electromagnet is a core of soft magnetic material surrounded by a coil of wire. An material surrounded by a coil of wire. An electric current is passed through the wire to electric current is passed through the wire to magnetize the core when a switch is flicked magnetize the core when a switch is flicked or a button is pushed. The device then has or a button is pushed. The device then has the power to attract iron objects. When the the power to attract iron objects. When the switch is turned off, the attraction is broken. switch is turned off, the attraction is broken. Electromagnets are used in radios and in Electromagnets are used in radios and in ordinary doorbells. (page 573)ordinary doorbells. (page 573)


Conductors and InsulatorsConductors and Insulators

Directions: Identify the following terms as Directions: Identify the following terms as either a conductor of electricity (C) or an either a conductor of electricity (C) or an insulator (I).insulator (I).

1. ________1. ________ leatherleather

2. ________2. ________ woodwood

3. ________ 3. ________ salt watersalt water

4. ________4. ________ plasticplastic

5. ________5. ________ coppercopper



Directions: Choose the best answer for the following Directions: Choose the best answer for the following questions.questions.

1. Why would a radio with a strong electromagnet be placed 1. Why would a radio with a strong electromagnet be placed far away from the navigation instruments on a plane or ship?far away from the navigation instruments on a plane or ship?

(1) The radio wouldn't work because of electrical interference.(1) The radio wouldn't work because of electrical interference.

(2) The radio couldn't be heard clearly because of static.(2) The radio couldn't be heard clearly because of static.

(3) The accuracy of the compass would be affected by the (3) The accuracy of the compass would be affected by the magnetic field established by the radio's electromagnet.magnetic field established by the radio's electromagnet.

(4) The radio's electromagnet would cause all the navigation (4) The radio's electromagnet would cause all the navigation instruments to malfunction.instruments to malfunction.

(5) The radio would draw too much electrical energy, causing (5) The radio would draw too much electrical energy, causing the electrical system of the ship or plane to discharge.the electrical system of the ship or plane to discharge.



2. Identify which of the following are true 2. Identify which of the following are true (T) or false (F).(T) or false (F).

___ You need an insulator to keep ___ You need an insulator to keep electricity flowing only along wires.electricity flowing only along wires.

___ Electromagnets are used in doorbells.___ Electromagnets are used in doorbells.

___ When the switch is in the off position, ___ When the switch is in the off position, electricity still is flowing through the electricity still is flowing through the circuit.circuit.


Creating ElectricityCreating Electricity

Electricity is created by power companies Electricity is created by power companies and sent to our homes by high voltage and sent to our homes by high voltage wires through transformers. There are wires through transformers. There are several ways to create electricity. Because several ways to create electricity. Because there is a concern about the limited there is a concern about the limited quantities of fossil fuels, alternative power quantities of fossil fuels, alternative power supplies for electricity are being used. supplies for electricity are being used. (page 575)(page 575)



One system requires the fission of nuclear One system requires the fission of nuclear energy in nuclear power plants. These energy in nuclear power plants. These plants bombard the nuclei of large plants bombard the nuclei of large unstable uranium atoms with neutrons. unstable uranium atoms with neutrons. The large release of heat is used to heat The large release of heat is used to heat water, which is used to turn a turbine, a water, which is used to turn a turbine, a wire loop connecting two magnets. (page wire loop connecting two magnets. (page 575)575)



When the turbine is forced to turn, the When the turbine is forced to turn, the electrons are stolen from the magnets and electrons are stolen from the magnets and sent through the wire as electricity. This sent through the wire as electricity. This alternative energy has many drawbacks, alternative energy has many drawbacks, including the safe disposal of radioactive including the safe disposal of radioactive nuclear waste left over from the reaction. nuclear waste left over from the reaction. (page 575)(page 575)



TURBINETURBINE

Physical SciencePhysical ScienceCreating ElectricityCreating Electricity

Another alternative is solar energy. Scientists Another alternative is solar energy. Scientists have found that pure silicon (found in sand and have found that pure silicon (found in sand and one of the most common elements in the crust one of the most common elements in the crust of the Earth) is electrically excited in the of the Earth) is electrically excited in the presence of light. You may have experienced presence of light. You may have experienced this if you own a solar calculator, but it may not this if you own a solar calculator, but it may not have performed in a dimly lighted area. The have performed in a dimly lighted area. The sun's energy excites the electrons, which then sun's energy excites the electrons, which then flow along wires to provide electricity to the flow along wires to provide electricity to the attached appliance. (page 575)attached appliance. (page 575)


SOLAR ENERGYSOLAR ENERGY


Other alternative energies are limited to Other alternative energies are limited to the availability of the conditions necessary the availability of the conditions necessary to generate electricity. One such to generate electricity. One such alternative is wind power, which has been alternative is wind power, which has been successfully captured through the use of successfully captured through the use of windmills throughout the history of windmills throughout the history of civilization. California has wind farms civilization. California has wind farms where many large windmills are connected where many large windmills are connected to generate electricity. (page 576)to generate electricity. (page 576)


These new models on the old design limit These new models on the old design limit the number of arms on the mill and make the number of arms on the mill and make these arms out of durable synthetic these arms out of durable synthetic materials. Windmills do not need a strong materials. Windmills do not need a strong wind; in fact, strong winds can damage wind; in fact, strong winds can damage the mechanics. The best condition is a the mechanics. The best condition is a steady wind that maintains a continuous steady wind that maintains a continuous motion of the flywheel. (page 576)motion of the flywheel. (page 576)


WIND ENERGYWIND ENERGY



Hydroelectric power is another source Hydroelectric power is another source that has to be limited to the already that has to be limited to the already established use of the water flow in the established use of the water flow in the region. Many rivers are used as region. Many rivers are used as transportation and cannot be dammed to transportation and cannot be dammed to provide the reservoir of water needed to provide the reservoir of water needed to control the flow of water through the control the flow of water through the turbine system. (page 576)turbine system. (page 576)



Yet hydroelectric power, as well as wind Yet hydroelectric power, as well as wind and solar powers is a clean, renewable and solar powers is a clean, renewable resource. Critics suggest that the reason resource. Critics suggest that the reason these systems have not been fully these systems have not been fully developed is the fear energy companies developed is the fear energy companies have in reducing their own incomes. have in reducing their own incomes. (page 576)(page 576)



Hydroelectric powerHydroelectric power


Creating Electricity (page 577)Creating Electricity (page 577)

Directions: Use the information above to fill in the blanks in Directions: Use the information above to fill in the blanks in each statement below.each statement below.

1. Hydroelectric power is not always possible because 1. Hydroelectric power is not always possible because sometimes rivers are used for _______________.sometimes rivers are used for _______________.

2. Fossil fuels will not be around forever, so we need to 2. Fossil fuels will not be around forever, so we need to explore the use of other energy systems called explore the use of other energy systems called _______________._______________.

3. Windmills do not need strong wind, but they do need 3. Windmills do not need strong wind, but they do need _______________ wind._______________ wind.

4. Pure silicon has electrons that are excited into motion by 4. Pure silicon has electrons that are excited into motion by _________________._________________.

5. A loop or wire that is turned between two magnets and 5. A loop or wire that is turned between two magnets and creates electricity is a _______________.creates electricity is a _______________.

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