MANUAL ELECTRICTY AND MAGNETISM

8/6/2019 MANUAL ELECTRICTY AND MAGNETISM

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Samar State UniversityCOLLEGE OF ARTS AND SCIENCES

Catbalogan City, Samar

REVIEW GUIDE-FINALSElectricity and Magnetism

CHAPTER IV. INTRODUCTION TO ELECTRICITYA. History of Electricity

600 BC- Ancient cultures around the Mediterranean knew that certain objects, suchas rods of amber, could be rubbed with cat's fur to attract light objects likefeathers. Thales of Miletos made a series of observations on static electricity.

1600- English scientist William Gilbert made a careful study of electricity andmagnetism, distinguishing the lodestone effect from static electricity producedby rubbing amber. He coined the New Latin word electricus ("of amber" or "likeamber", from [elektron], the Greek word for "amber") to refer to theproperty of attracting small objects after being rubbed.

1729- Stephen Gray discovered the principle of the conduction of electricity

1733, Charles Francois du Fay discovered that electricity comes in two forms whichhe called resinous (-) and vitreous (+), now called negative and positive.

1752- Ben Franklin's important discovery was that electricity and lightning were oneand the same. Ben Franklin's lightning rod was the first practical application ofelectricity.

1786- Italian physician, Luigi Galvani demonstrated what we now understand to bethe electrical basis of nerve impulses when he made frog muscles twitch byjolting them with a spark from an electrostatic machine.

1800- First electric battery invented by Alessandro Volta. Volta proved that electricitycould travel over wires.

1820- Relationship of electricity and magnetism confirmed by Hans Christian Oersted

who observed that electrical currents effected the needle on a compass andMarie Ampere, who discovered that a coil of wires acted like a magnet when acurrent is passed through it.

1821- First electric motor invented by Michael Faraday.1826- Ohms Law written by Georg Simon Ohm states that "conduction law that

relates potential, current, and circuit resistance"1831- Principles of electromagnetism induction, generation and transmission

discovered by Michael Faraday.1873- James Clerk Maxwell wrote equations that described the electromagnetic field,

and predicted the existence of electromagnetic waves traveling with the speedof light. Electromagnetism as a field of Physics was born.

1879- Thomas Edison demonstrates his incandescent lamp, Menlo Park, New Jersey.1882- Edison Company opens Pearl Street power station. The first hydroelectric

power station opens in Wisconsin.

B. The Electrical AtomThe atom, the fundamental unit of matter (element), has two major regions.The region or area where the neutron and proton are located is known as thenucleus; while the outermost region or area where electrons are located isknown as the electron cloud. Atoms are therefore made up of 3 types ofelementary particles electrons, protons and neutrons. These particles have


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different properties. Electrons are tiny, very light particles that have anegative electrical charge (-). Protons are much larger and heavier thanelectrons and have the opposite charge, protons have a positive charge(+). Neutrons are large and heavy like protons; however neutrons have noelectrical charge. Each atom is made up of a combination of theseparticles. An atom is usually made of equal number of protons and electronsmaking the atom neutrally charged. When electrons are emitted, the atom

becomes positively charged. When atoms absorb electrons, there is moreelectron than protons leading the atoms to become negatively charged.

C. Charging by Induction and Charging by ConductionCharging by Conduction

Conductionjust means that the two objects will come into actual physicalcontact with each other (this is why it is sometimes called charging bycontact). Given a negatively charged metal object and an uncharged metal sphere.The uncharged sphere is on an insulating stand so that it will not interact withanything else. Bringing the two objects close together will cause separation of

charge in the neutral object as negative electrons are repelled from thepositive charges. At this time, they are not touching between the chargedmetal object and the neutral metal ball and no charges have been transferredyet. Allowing the two objects to touch, some of the negative charge willtransfer over to the uncharged metal object. This happens since the negativecharges on the first object are repelling each other and by moving onto thesecond object they spread away from each other. When the negative object isremoved, it will not be as negative as it was. Both of the objects have some ofthe negative charge how much depends on the size of the objects and thematerials they are made of. If they are the same size, made of the samematerials, then the charge will be the same on both.

Charging by InductionIt is possible to charge a conductor without coming into direct contact with it. The most important one is the use of a grounding wire. A grounding wire is simply a conductor that connects the object to theground. Think of the earth as a huge reservoir of charge it can both gain or donateelectrons as needed. Depending on what the situation is, either electrons willtravel up the grounding wire to the object being charged, or travel down tothe ground. Charging by induction is a more complex process than conduction

D. Conductors and Insulators

The electrons of different types of atoms have different degrees offreedom to move around. With some types of materials, such as metals, theoutermost electrons in the atoms are so loosely bound that they chaoticallymove in the space between the atoms of that material by nothing more thanthe influence of room-temperature heat energy. Because these virtuallyunbound electrons are free to leave their respective atoms and float around inthe space between adjacent atoms, they are often called free electrons.

In other types of materials such as glass, the atoms' electrons have verylittle freedom to move around. While external forces such as physical rubbingcan force some of these electrons to leave their respective atoms and transfer


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to the atoms of another material, they do not move between atoms within thatmaterial very easily.

This relative mobility of electrons within a material is known aselectric conductivity. Conductivity is determined by the types of atoms in amaterial (the number of protons in each atom's nucleus, determining itschemical identity) and how the atoms are linked together with one another.Materials with high electron mobility (many free electrons) are

calledconductors, while materials with low electron mobility (few or no freeelectrons) are called insulators.Here are a few common examples of conductors and insulators:

Conductors: (arrange according to decreasing level of conductivity) silver copper gold aluminum iron steel brass

bronze mercury graphite dirty water concrete

Insulators: (arranged according to decreasing level of resistivity) glass rubber oil asphalt fiberglass

porcelain ceramic quartz (dry) cotton (dry) paper (dry) wood plastic air diamond pure water

It must be understood that not all conductive materials have the samelevel of conductivity, and not all insulators are equally resistant to electronmotion. Electrical conductivity is analogous to the transparency of certainmaterials to light: materials that easily "conduct" light are called "transparent,"while those that don't are called "opaque." However, not all transparentmaterials are equally conductive to light. Window glass is better than mostplastics, and certainly better than "clear" fiberglass. So it is with electricalconductors, some being better than others.

For instance, silver is the best conductor in the "conductors" list, offeringeasier passage for electrons than any other material cited. Dirty water and


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concrete are also listed as conductors, but these materials are substantiallyless conductive than any metal.

A. Coulomb's Law

The quantitative expression for the effect of these three variables onelectric force is known as Coulomb's law. Coulomb's law states that theelectrical force between two charged objects is directly proportional to the

product of the quantity of charge on the objects and inversely proportional tothe square of the separation distance between the two objects. In equationform, Coulomb's law can be stated as

where Q1 represents the quantity of charge on object 1 (inCoulombs), Q2 represents the quantity of charge on object 2 (in Coulombs),and d represents the distance of separation between the two objects (inmeters). The symbolkis a proportionality constant known as the Coulomb's lawconstant. The value of this constant is dependent upon the medium that thecharged objects are immersed in. In the case of air, the value is approximately9.0 x 109 N m2 / C2. If the charged objects are present in water, the valueofkcan be reduced by as much as a factor of 80. It is worthwhile to point outthat the units on kare such that when substituted into the equation the unitson charge (Coulombs) and the units on distance (meters) will be canceled,leaving a Newton as the unit of force.

The Coulomb's law equation provides an accurate description of the forcebetween two objects whenever the objects act as point charges. A chargedconducting sphere interacts with other charged objects as though all of itscharge were located at its center. While the charge is uniformly spread acrossthe surface of the sphere, the center of charge can be considered to be thecenter of the sphere. The sphere acts as a point charge with its excess chargelocated at its center. Since Coulomb's law applies to point charges, thedistance d in the equation is the distance between the centers of charge forboth objects (not the distance between their nearest surfaces).

The symbolsQ1 and Q2 in the Coulomb's law equation represent thequantities of charge on the two interacting objects. Since an object can becharged positively or negatively, these quantities are often expressed as "+" or

"-" values. The sign on the charge is simply representative of whether theobject has an excess of electrons (a negatively charged object) or a shortage ofelectrons (a positively charged object). It might be tempting to utilize the "+"and "-" signs in the calculations of force. While the practice is notrecommended, there is certainly no harm in doing so. When using the "+" and"-" signs in the calculation of force, the result will be that a "-" value for force isa sign of an attractive force and a "+" value for force signifies a repulsive force.Mathematically, the force value would be found to be positivewhen Q1 and Q2 are of like charge - either both "+" or both "-". And the forcevalue would be found to be negative when Q1 and Q2 are of opposite charge -


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one is "+" and the other is "-". This is consistent with the concept thatoppositely charged objects have an attractive interaction and like chargedobjects have a repulsive interaction. In the end, if you're thinking conceptually(and not merely mathematically), you would be very able to determine thenature of the force - attractive or repulsive - without the use of "+" and "-"signs in the equation.

CHAPTER V. ELECTRIC CURRENTA. Basic Electrical Quantities

Voltage is the potential energy of an electrical supply stored in the formof an electrical charge. Voltage can be thought of as the force that pusheselectrons through a conductor and the greater the voltage the greater is itsability to "push" the electrons through a given circuit. As energy has the abilityto do work this potential energy can be described as the work required in joulesto move electrons in the form of an electrical current around a circuit from onepoint or node to another. The difference in voltage between any two nodes in acircuit is known as the Potential Difference, p.d. sometimes called Voltage

Drop.The Potential difference between two points is measured in Volts with

the circuit symbol V, or lowercase "v", although Energy, E lowercase "e" issometimes used. Then the greater the voltage, the greater is the pressure (orpushing force) and the greater is the capacity to do work.

A constant voltage source is called a DC Voltage with a voltage thatvaries periodically with time is called an AC voltage. Voltage is measured involts, with one volt being defined as the electrical pressure required to force anelectrical current of one ampere through a resistance of one Ohm. Voltages aregenerally expressed in Volts with prefixes used to denote sub-multiples of thevoltage such asmicrovolts ( V = 10-6 V ), millivolts ( mV = 10-3 V )

or kilovolts ( kV = 103 V ). Voltage can be either positive or negative.Batteries or power supplies are mostly used to produce a steady D.C.

(direct current) voltage source such as 5v, 12v, 24v etc in electronic circuitsand systems. While A.C. (alternating current) voltage sources are available fordomestic house and industrial power and lighting as well as powertransmission. The mains voltage supply in the United Kingdom is currently 230volts a.c. and 110 volts a.c. in the USA. General electronic circuits operate onlow voltage DC battery supplies of between 1.5V and 24V d.c. The circuitsymbol for a constant voltage source usually given as a battery symbol with apositive, + and negative, - sign indicating the direction of the polarity. Thecircuit symbol for an alternating voltage source is a circle with a sine wave

inside.Voltage Symbols


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A simple relationship can be made between a tank of water and a voltagesupply. The higher the water tank above the outlet the greater the pressure ofthe water as more energy is released, the higher the voltage the greater thepotential energy as more electrons are released. Voltage is always measuredas the difference between any two points in a circuit and the voltage betweenthese two points is generally referred to as the "Voltage drop". Any voltagesource whether DC or AC likes an open or semi-open circuit condition but hatesany short circuit condition as this can destroy it.

Electrical Current is the movement or flow of electrical charge and ismeasured in Amperes, symbol i, for intensity). It is the continuous anduniform flow (called a drift) of electrons (the negative particles of an atom)around a circuit that are being "pushed" by the voltage source. In reality,electrons flow from the negative (-ve) terminal to the positive (+ve) terminal ofthe supply and for ease of circuit understanding conventional current flowassumes that the current flows from the positive to the negative terminal.Generally in circuit diagrams the flow of current through the circuit usually hasan arrow associated with the symbol, I, or lowercase i to indicate the actualdirection of the current flow. However, this arrow usually indicates the directionof conventional current flow and not necessarily the direction of the actualflow.

Conventional Current FlowConventionally this is the flow of positive charge

around a circuit. The diagram at the left shows themovement of the positive charge (holes) which flowsfrom the positive terminal of the battery, through thecircuit and returns to the negative terminal of thebattery. This was the convention chosen during thediscovery of electricity in which the direction ofelectric current was thought to flow in a circuit. Incircuit diagrams, the arrows shown on symbols for

components such as diodes and transistors point in the direction ofconventional current flow. Conventional Current Flow is the opposite in

direction to the flow of electrons.Electron Flow The flow of electrons around the circuit is

opposite to the direction of the conventional currentflow. The current flowing in a circuit is composed ofelectrons that flow from the negative pole of thebattery (the cathode) and return to the positive pole


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(the anode). This is because the charge on an electron is negative by definitionand so is attracted to the positive terminal. The flow of electrons iscalled Electron Current Flow. Therefore, electrons flow from the negativeterminal to the positive.

Both conventional current flow and electron flow are used by manytextbooks. In fact, it makes no difference which way the current is flowingaround the circuit as long as the direction is used consistently. The direction of

current flow does not affect what the current does within the circuit. Generallyit is much easier to understand the conventional current flow - positive tonegative.

In electronic circuits, a current source is a circuit element that provides aspecified amount of current for example, 1A, 5A 10 Amps etc, with the circuitsymbol for a constant current source given as a circle with an arrow insideindicating its direction. Current is measured in Amps and an amp or ampere isdefined as the number of electrons or charge (Q in Coulombs) passing a certainpoint in the circuit in one second, (t in Seconds). Current is generally expressedin Amps with prefixes used to denote micro amps (A = 10-6A) or milliamps (mA = 10-3A). Electrical current can be either positive or negative.

Current that flows in a single direction is called Direct Current,or D.C. and current that alternates back and forth through the circuit is knownas Alternating Current, or A.C.. Whether AC or DC current only flows througha circuit when a voltage source is connected to it with its "flow" being limited toboth the resistance of the circuit and the voltage source pushing it. Also, as ACcurrents (and voltages) are periodic and vary with time the "effective" or"RMS", (Root Mean Squared) value given as Irms produces the same averagepower loss equivalent to a DC current Iaverage . Current sources are the oppositeto voltage sources in that they like short or closed circuit conditions but hateopen circuit conditions as no current will flow.

Using the tank of water relationship, current is the equivalent of the flow

of water through the pipe with the flow being the same throughout the pipe.The faster the flow of water the greater the current. Any current sourcewhether DC or AC likes a short or semi-short circuit condition but hates anyopen circuit condition as this prevents it from flowing.

The Resistance of a circuit is its ability to resist or prevent the flow ofcurrent (electron flow) through it making it necessary to apply a bigger voltageto the circuit to cause the current to flow again. Resistance is measuredin Ohms, Greek symbol ( , Omega ) with prefixes used to denote Kilo-ohms (k = 103) and Mega-ohms (M = 106). Resistance cannot benegative only positive.

Resistor Symbols


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The amount of resistance determines whether the circuit is a "good conductor"- low resistance, or a "bad conductor" - high resistance. Low resistance, forexample 1 or less implies that the circuit is a good conductor made frommaterials such as copper, aluminium or carbon while a high resistance, 1M ormore implies the circuit is a bad conductor made from insulating materialssuch as glass, porcelain or plastic. A "semiconductor" on the other hand suchas silicon or germanium, is a material whose resistance is half way betweenthat of a good conductor and a good insulator. Semiconductors are used tomake Diodes and Transistors etc.

Again, using the water relationship, resistance is the diameter or thelength of the pipe the water flows through. The smaller the diameter of thepipe the larger the resistance to the flow of water, and therefore the larger theresistance. However, it is not just the diameter or the cross-sectional area ofthe wire that affects the resistance of the material to the flow of current. Also afactor is the length of the wire, the longer the wire the higher the resistance,the shorter the wire the lower the resistance. Another factor is the kind ofmaterial used as a wire, conductors have lower resistance than the insulators.Temperature can also affect the resistance. The higher the temperature thehigher the resistance the lower the temperature the lower the resistance.

Quantity Symbol Unit ofMeasure

Abbreviation

Voltage V orE Volt V

Current I Amperes A

Resistance R Ohms

B. Ohms Law

Ohms Law states that current is proportional to voltage and inverselyproportional to the resistance. Ohm's Law shows the relationship between thevoltage (V), current (I) and resistance (R). It can be written in three ways:

V = I R

orI=

V

R

orR=

V

I

where:

V = voltage in volts(V)

or:

V = voltage in volts (V)I = current in milliamps
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I = current in amps(A)R = resistance inohms ( )

(mA)R = resistance in kilohms(k )

For most electronic circuits the amp is too large and the ohm is too small,so we often measure current in milliamps (mA) and resistance in kilohms (k ).

1 mA = 0.001 A and 1 k = 1000 .

The Ohm's Law equations work if you use V, A and , or if you use V, mAand k . You must not mix these sets of units in the equations so you may needto convert between mA and A or k and .

C. Series and Parallel ConnectionComponents of an electrical circuit or electronic circuit can be connected

in many different ways. The two simplest of these arecalled series and parallel and occur very frequently. Components connectedin series are connected along a single path, so the same current flows throughall of the components. Components connected in parallel are connected so the

same voltage is applied to each component.A circuit composed solely of components connected in series is known as

a series circuit; likewise, one connected completely in parallel is known asa parallel circuit.

In a series circuit , the current through each of the components is thesame, and the voltage across the components is the sum of the voltagesacross each component. In a parallel circuit, the voltage across each of thecomponents is the same, and the total current is the sum of the currentsthrough each component.

D. Ammeter and Voltmeter

In terms of external connections Ammeter (used to measure current) isconnected in series of the circuit (through which the current flow need to bemeasured) and voltmeter (used to measure voltage) is connected in parallel topoints in circuit (across which voltage needs to be measured).E. Circuit Symbols

Refer to your copies

F. Effects of Electrical Current on Human BodyRefer to your copies

G. Household Electrical ConsumptionRefer to your copies

CHAPTER VI. MAGNETISMA. History of Magnetism

600 BC - LodestoneThe magnetic properties of natural ferric ferrite (Fe3O4) stones

(lodestones) were described by Greek philosophers.
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1600 - Static Electricity (De Magnete)

In the 16th century, William Gilbert(1544-1603), the Court Physician toQueen Elizabeth I, Gilbert also studied magnetism and in 1600 wrote "Demagnete" which gave the first rational explanation to the mysterious ability ofthe compass needle to point north-south: the Earth itself was magnetic. "DeMagnete" opened the era of modern physics and astronomy and started acentury marked by the great achievements of Galileo, Kepler, Newton and

others. Gilbert recorded three ways to magnetize a steel needle: by touch witha loadstone; by cold drawing in a North-South direction; and by exposure for along time to the Earth's magnetic field while in a North-South orientation.

1730 - Compound MagnetServigton Savery produces the first compound magnet by binding

together a number of artificial magnets with a common pole piece at each end.1740 - First Commercial Magnet

Gowen Knight produces the first artificial magnets for sale to scientificinvestigators and terrestrial navigators.

1750 - First Book on Magnet Manufacture

John Mitchell publishes the first book on making steel magnets.1820 - Electromagnetism, Current

In 1820, a physicist Hans Christian Oersted, learned thata current flowing through a wire would move a compass needle placed besideit. This showed that an electric current produced a magnetic field. Andre MarieAmpere, a French mathematician who devoted himself to the study ofelectricity and magnetism, was the first to explain the electro-dynamic theory.He showed that two parallel wires, carrying current, attracted each other if thecurrents flowed in the same direction and opposed each other if the currentsflowed in opposite directions. He formulated in mathematical terms, the lawsthat govern the interaction of currents with magnetic fields in a circuit and as aresult of this the unit of electric current, the amp, was derived from his name.An electric charge in motion is called electric current. The strength of a currentis the amount of charge passing a given point per second, or I = Q/t, where Qcoulombs of charge passing in t seconds. The unit for measuring currentisthe ampere or amp, where 1 amp = 1 coulomb/sec. Because it is the source ofmagnetism as well, current is the link between electricity and magnetism.1855 - Electromagnetic Induction

Michael Faraday (1791-1867) an Englishman, made one of the mostsignificant discoveries in the history of electricity: Electromagnetic induction.His pioneering work dealt with how electric currents work. Many inventionswould come from his experiments, but they would come fifty to one hundredyears later. Failures never discouraged Faraday. He would say; "the failures arejust as important as the successes." He felt failures also teach. The farad,the unit of capacitance is named in the honor of Michael Faraday.

Faraday was greatly interested in the invention of the electromagnet, buthis brilliant mind took earlier experiments still further. If electricity couldproduce magnetism, why couldn't magnetism produce electricity. In 1831,Faraday found the solution. Electricity could be produced through magnetismby motion. He discovered that when a magnet was moved inside a coil ofcopper wire, a tiny electric current flows through the wire. H.C. Oersted, in


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1820, demonstrated that electric currents produce a magnetic field. Faradaynoted this and in 1821, he experimented on the theory that, if electric currentsin a wire can produce magnetic fields, then magnetic fields should produceelectricity. By 1831, he was able to prove this and through his experiment, wasable to explain, that these magnetic fields were lines of force. These lines offorce would cause a current to flow in a coil of wire, when the coil is rotatedbetween the poles of a magnet. This action then shows that the coils of wire

being cut by lines of magnetic force, in some strange way, produces electricity.These experiments, convincingly demonstrated the discoveryof electromagnetic induction in the production of electric current, by a changein magnetic intensity.

1860:James Clerk Maxwell (1831-1879), a Scottish physicist andmathematician, puts the theory of electromagnetism on mathematical basis.

1873: Maxwell publishes "Treatise on Electricity and Magnetism" in whichhe summarizes and synthesizes the discoveries of Coloumb, Oersted, Ampere,Faraday, et. al. in four mathematical equations. Maxwell's Equations are usedtoday as the basis of electromagnetic theory. Maxwell makes a prediction

about the connections of magnetism and electricity leading directly to theprediction of electromagnetic waves.

1885: Heinrich Hertz shows Maxwell was correct and generates anddetects electromagnetic waves.

1895: Guglielmo Marconi puts the discovery to practical use by sendingmessages over long distances by means of radio signals. i.e. the "Wireless".

B. Magnetic Behaviorand Properties

Magnetism is the force of attraction or repulsion in a material. Certainmaterials such as iron, steel, nickel, or magnetite exhibit this force while mostother materials do not. A magnet is any piece of iron, steel, or magnetite that

has the property of attracting iron or steel. Magnets have two poles, called thenorth (N) and south (S) poles. Two magnets will be attacted by their oppositepoles, and each will repel the like pole of the other magnet. Magnets can be ofthe following form, U magnets, horseshoe magnets, bar magnets, and circularmagnets. Magnets which are controlled by electricity are known aselectromagnets. Magnetite, also known as lodestone, is a naturally occurringrock that is a magnet. This natural magnet was first discovered in a regionknown as Magnesia, Greece and was named after the area in which it wasdiscovered. Magnetism may be naturally present in a material or the materialmay be artificially magnetized by various methods. Magnets may bepermanent or temporary. After being magnetized, a permanent magnet will

retain the properties of magnetism indefinitely. A temporary magnet is amagnet made of soft iron, that is usually easy to magnetize; however,temporary magnets lose most of their magnetic properties when themagnetizing cause is discontinued. Permanent magnets are usually moredifficult to magnetize, but they remain magnetized. Materials which can bemagnetized are called ferromagnetic materials.

C. Magnetic DomainA magnetic domain is region in which the magnetic fields of atoms are

grouped together and aligned. In the experiment below, the magnetic domains
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are indicated by the arrows in the metal material. You can think of magneticdomains as miniature magnets within a material. In an unmagnetized object,like the initial piece of metal in our experiment, all the magnetic domains arepointing in different directions. But, when the metal became magnetized, whichis what happens when it is rubbed with a strong magnet, all like magnetic poleslined up and pointed in the same direction. The metal became a magnet. Itwould quickly become unmagnetized when its magnetic domains returned to a

random order. The metal in our experiment is a soft ferromagnetic material,which means that it is easily magnetized but may not retain its magnetismvery long.

D. Magnetic Lines of Force (Flux) and Field The lines that we have mapped out around the magnet, called

the magnetic lines of force (Flux), indicate the region in which the force ofthe magnet can be detected. This region is called the magnetic field. If aniron object is near a magnet, but is not within the magnetic field, the object willnot be attracted to the magnet. When the object enters the magnetic field, theforce of the magnet acts, and the object is attracted. The pattern of these lines

of force tells us something about the characteristics of the forces caused bythe magnet. The magnetic lines of force, or flux, leave the North Pole and enterthe South Pole.

E. Ferromagnetic MaterialsA permanent magnet is more difficult to magnetize but will retain the

properties of magnetism indefinitely. A temporary magnet is generally made ofsoft iron and will remain magnetized only as long as the magnetizing cause ispresent. From previous experiments you saw how the difference in magnetizedand unmagnetized material depends on the motion and arrangement of thematerial's molecules. Bringing a ferromagnetic object, like a nail, into the

magnetic field of a strong magnet can cause the molecules of the iron materialto line up and the nail to become a temporary magnet. As long as it is in themagnetic field of the bar magnet, the nail acts like a magnet and picks upother ferromagnetic materials. In this case it is the paper clip. Then, the paperclip becomes a magnet and can pick up another paper clip, and so forth.

F. ElectromagnetsIn this experiment you used electricity to make a temporary magnet,

called an electromagnet. As long as the electric current was on, the ironcrane was a magnet and could pick up ferromagnetic objects. When theelectricity was turned off, the magnetizing cause was no longer present, so the

object was not attracted to the iron crane. So, let's see how electricity is ableto make a magnet.

G. Electricity and MagnetismElectromagnetism is one of the four fundamental interactions of

nature. The other three are the strong interaction, the weakinteraction and gravitation. Electromagnetism is the force that causes theinteraction between electrically charged particles; the areas in which thishappens are called electromagnetic fields.
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Electromagnetism is responsible for practically all the phenomenaencountered in daily life, with the exception of gravity. Ordinary matter takesits form as a result ofintermolecular forces between individual molecules inmatter. Electromagnetism is also the force which holds electrons andprotons together inside atoms, which are the building blocks of molecules.

Electromagnetism manifests as both electric fields and magnetic fields.Both fields are simply different aspects of electromagnetism, and hence are

intrinsically related. Thus, a changing electric field generates a magnetic field;conversely a changing magnetic field generates an electric field. This effect iscalled electromagnetic induction, and is the basis of operation for electricalgenerators, induction motors, and transformers.

Electric fields are the cause of several common phenomena, suchas electric potential (such as the voltage of a battery) and electriccurrent (such as the flow of electricity through a flashlight). Magnetic fields arethe cause of the force associated with magnets.
http://en.wikipedia.org/wiki/Intermolecular_forcehttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Protonhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Faraday's_law_of_inductionhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Induction_motorhttp://en.wikipedia.org/wiki/Transformerhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electric_potentialhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Magnethttp://en.wikipedia.org/wiki/Intermolecular_forcehttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Protonhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Faraday's_law_of_inductionhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Induction_motorhttp://en.wikipedia.org/wiki/Transformerhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electric_potentialhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Magnet

MANUAL ELECTRICTY AND MAGNETISM

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