Physics 2

90
07/05/22 Physics 2 Physics 2 W Richards The Weald School

Transcript of Physics 2

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Physics 2Physics 2W Richards

The Weald School

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Distance, Speed Distance, Speed and Timeand Time

Speed = distance (in metres) time (in seconds)

D

TS

1) Seb walks 200 metres in 40 seconds. What is his speed?

2) Lucy covers 2km in 1,000 seconds. What is her speed?3) How long would it take Freddie to run 100 metres if he

runs at 10m/s?4) Sue travels at 50m/s for 20s. How far does he go?5) Hannah drives her car at 85mph (about 40m/s). How

long does it take her to drive 20km?

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Distance-time graphsDistance-time graphs

40

30

20

10

0 20 40 60 80 100

4) Diagonal line

downwards =

3) Steeper diagonal line =1) Diagonal line =

2) Horizontal line =

Distance

(metres)

Time/s

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40

30

20

10

0 20 40 60 80 100

1) What is the speed during the first 20 seconds?2) How far is the object from the start after 60 seconds?3) What is the speed during the last 40 seconds?4) When was the object travelling the fastest?

Distance

(metres)

Time/s

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Speed vs. VelocitySpeed vs. Velocity

Speed is simply how fast you are travelling…

Velocity is “speed in a given direction”…

This car is travelling at a speed of 20m/s

This car is travelling at a velocity of 20m/s east

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AccelerationAcceleration V-U

TAAcceleration = change in velocity (in m/s) (in m/s2) time taken (in s)1) A cyclist accelerates from 0 to 10m/s in 5 seconds.

What is her acceleration?2) A ball is dropped and accelerates downwards at a rate

of 10m/s2 for 12 seconds. How much will the ball’s velocity increase by?

3) A car accelerates from 10 to 20m/s with an acceleration of 2m/s2. How long did this take?

4) A rocket accelerates from 1,000m/s to 5,000m/s in 2 seconds. What is its acceleration?

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Velocity-time graphsVelocity-time graphs

80

60

40

20

0 10 20 30 40 50

Velocity

m/s

T/s

1) Upwards line =

2) Horizontal line =

3) Upwards line =

4) Downward line =

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80

60

40

20

0

1) How fast was the object going after 10 seconds?2) What is the acceleration from 20 to 30 seconds?3) What was the deceleration from 30 to 50s?4) How far did the object travel altogether?

10 20 30 40 50

Velocity

m/s

T/s

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Balanced and unbalanced Balanced and unbalanced forcesforces

Consider a camel standing on a road. What forces are acting on it?

Weight

Reaction

These two forces would be equal – we say that they are BALANCED. The camel doesn’t move anywhere.

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Balanced and unbalanced Balanced and unbalanced forcesforces

What would happen if we took the road away?

Weight

Reaction

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Balanced and unbalanced Balanced and unbalanced forcesforces

What would happen if we took the road away?

The camel’s weight is no longer balanced by anything, so the camel falls downwards…

Weight

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What would happen if we took the road away?

The camel’s weight is no longer balanced by anything, so the camel falls downwards…

Balanced and unbalanced Balanced and unbalanced forcesforces

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Air ResistanceAir ResistanceAir resistance is a force that opposes motion through air. The quicker you travel, the bigger the air resistance:

The same applies to a body falling through a liquid (called “drag” or “upthrust”).

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Balanced and unbalanced Balanced and unbalanced forcesforces

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Balanced and unbalanced Balanced and unbalanced forcesforces

1) This animal is either ________ or moving with _____ _____…

4) This animal is…

2) This animal is getting _________…

3) This animal is getting _______….

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Resultant ForceResultant ForceCalculate the resultant force of the following:

500N 100N 700N 600N

700N 700N

200N

800N 800N

100N

50N

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Force and accelerationForce and accelerationIf the forces acting on an object are unbalanced then the object will accelerate, like these wrestlers:

Force (in N) = Mass (in kg) x Acceleration (in m/s2)

F

AM

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Force, mass and accelerationForce, mass and acceleration1) A force of 1000N is applied to

push a mass of 500kg. How quickly does it accelerate?

2) A force of 3000N acts on a car to make it accelerate by 1.5m/s2. How heavy is the car?

3) A car accelerates at a rate of 5m/s2. If it weighs 500kg how much driving force is the engine applying?

4) A force of 10N is applied by a boy while lifting a 20kg mass. How much does it accelerate by?

F

AM

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Terminal VelocityTerminal VelocityConsider a skydiver:1) At the start of his jump the air

resistance is _______ so he _______ downwards.

2) As his speed increases his air resistance will _______

3) Eventually the air resistance will be big enough to _______ the skydiver’s weight. At this point the forces are balanced so his speed becomes ________ - this is called TERMINAL VELOCITY

Words – increase, small, constant, balance,

accelerates

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Terminal Terminal VelocityVelocity

Consider a skydiver:

4) When he opens his parachute the air resistance suddenly ________, causing him to start _____ ____.

5) Because he is slowing down his air resistance will _______ again until it balances his _________. The skydiver has now reached a new, lower ________ _______.

Words – slowing down, decrease, increases, terminal

velocity, weight

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Velocity-time graph for terminal Velocity-time graph for terminal velocity…velocity…

Velocity

Time

Speed increases…

Terminal velocity reached…

Parachute opens – diver slows down

New, lower terminal velocity reached

Diver hits the ground

On the Moon

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Weight vs. MassWeight vs. MassEarth’s Gravitational Field Strength is 10N/kg. In other

words, a 1kg mass is pulled downwards by a force of 10N.

W

gM

Weight = Mass x Gravitational Field Strength (in N) (in kg) (in N/kg)

1) What is the weight on Earth of a book with mass 2kg?2) What is the weight on Earth of an apple with mass 100g?3) Dave weighs 700N. What is his mass?4) On the moon the gravitational field strength is 1.6N/kg. What will

Dave weigh if he stands on the moon?

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Stopping a car…Stopping a car…

Braking distance

Too much alcoholThinking

distance

(reaction time)

Tiredness

Too many drugs

Wet roads

Driving too fast

Tyres/brakes worn out

Icy roads

Poor visibility

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Work doneWork doneWhen any object is moved around work will need to be done on it to get it to move (obviously).

We can work out the amount of work done in moving an object using the formula:

Work done = Force x distance moved

in J in N in mW

DF

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Example questionsExample questions1. Bori pushes a book 5m along the table with a force of

5N. He gets tired and decides to call it a day. How much work did he do?

2. Alicia lifts a laptop 2m into the air with a force of 10N. How much work does she do?

3. Martin does 200J of work by pushing a wheelbarrow with a force of 50N. How far did he push it?

4. Chris cuddles his cat and lifts it 1.5m in the air. If he did 75J of work how much force did he use?

5. Carl drives his car 1000m. If the engine was producing a driving force of 2000N how much work did the car do?

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Elastic Potential EnergyElastic Potential Energy

Elastic potential energy is the energy stored in a system when work is done to change its shape, e.g:

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Kinetic energyKinetic energyAny object that moves will have kinetic energy.

The amount of kinetic energy an object has can be found using the formula:

Kinetic energy = ½ x mass x velocity squaredin J in kg in m/s

KE = ½ mv2

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Example questionsExample questions1) Nicole drives her car at a speed of 30m/s. If the

combined mass of her and the car is 1000kg what is her kinetic energy?

2) Shanie rides her bike at a speed of 10m/s. If the combined mass of Shanie and her bike is 80kg what is her kinetic energy?

3) Dan is running and has a kinetic energy of 750J. If his mass is 60kg how fast is he running?

4) George is walking to town. If he has a kinetic energy of 150J and he’s walking at a pace of 2m/s what is his mass?

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Random questions…Random questions…1) Sophie tries to run 100m in 12 seconds and succeeds. How fast

did she run?2) Tommy accelerates at a rate of 2m/s2 for 3 seconds. If he started

at 10m/s what was his final speed?3) Charlie decides to lift his book up into the air. His book has a

mass of 100g and he lifts it 50cm. Calculate the work done.4) Lewis accelerates from 0 to 10m/s in 5 seconds. If his mass is

70kg how much force did his legs apply?5) Rachel rides 1km at a speed of 20m/s. How long did the journey

take?6) Claire thinks it’s funny to push James with a force of 120N. If

James has a mass of 60kg calculate his acceleration.7) Lauren slams on the brakes on her bike and her brakes do 20,000J

of work. If the combined mass is 100kg what speed was she travelling at?

8) Tom has a mass of 75kg. If he accelerates from 10 to 20m/s in 2s how much force did he apply?

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Random questions…Random questions…9) Georgina amuses herself by throwing things at Sarah. If she

throws a ball with a speed of 20m/s and the distance between her and Sarah is 5m how long will it take to reach her?

10)Mr Richards throws calculators around the room with a force of 20N. If each calculator has a mass of 200g calculate the acceleration.

11)Sam has a mass of 70kg. What is his weight on Earth, where the gravitational field strength is 10N/kg?

12)Zak does some work by pushing a box around with a force of 1N. He does 5J of work and decides to call it a day. How far did he push it?

13)On the moon Matt might weigh 112N. If the gravitational field strength on the moon is 1.6N/kg what is his mass? What will he weigh on Earth?

14)Dan likes bird watching. He sees a bird fly 100m in 20s. How fast was it flying?

15)How much kinetic energy would Richard have if he travelled at a speed of 5m/s and has a mass of 70kg?

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MomentumMomentumAny object that has both mass and velocity has MOMENTUM. Momentum (symbol “p”) is simply given by the formula:

Momentum = Mass x Velocity (in kgms-1) (in kg) (in ms-

1)

P

VM

What is the momentum of the following?1) A 1kg football travelling at 10ms-1

2) A 1000kg Ford Capri travelling at 30ms-1

3) A 20g pen being thrown across the room at 5ms-1

4) A 70kg bungi-jumper falling at 40ms-1

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Conservation of MomentumConservation of MomentumIn any collision or explosion momentum is conserved (provided that there are no external forces have an effect). Example question:

Two cars are racing around the M25. Car A collides with the back of car B and the cars stick together. What speed do they move at after the collision?

Mass = 1000kg

Mass = 800kgSpeed = 50ms-1 Speed = 20ms-1

Momentum before = momentum after……so 1000 x 50 + 800 x 20 = 1800 x V…

…V = 36.7ms-1

Mass = 1800kg

Speed = ??ms-1

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Momentum in different directionsMomentum in different directionsWhat happens if the bodies are moving in opposite directions?

Speed = 50ms-1

Mass = 1000kg

Speed = 20ms-1

Mass = 800kg

Momentum is a VECTOR quantity, so the momentum of the second car is negative…

Total momentum = 1000 x 50 – 800 x 20 = 34000 kgms-1

Speed after collision = 34000 kgms-1 / 1800 = 18.9ms-1

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Another exampleAnother exampleConsider the nuclear decay of Americium-241:

Am24195

α42

If the new neptunium atom moves away at a speed of 5x105 ms-1 what was the speed of the alpha particle?

Np23793

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More questions…More questions…1) A white snooker ball moving at 5m/s strikes a red ball and pots it.

Both balls have a mass of 1kg. If the white ball continued in the same direction at 2m/s what was the velocity of the red ball?

2) A car of mass 1000kg heading up the M1 at 50m/s collides with a stationary truck of mass 8000kg and sticks to it. What velocity does the wreckage move forward at?

3) A defender running away from a goalkeeper at 5m/s is hit in the back of his head by the goal kick. The ball stops dead and the player’s speed increases to 5.5m/s. If the ball had a mass of 500g and the player had a mass of 70kg how fast was the ball moving?

4) A gun has a recoil speed of 2m/s when firing. If the gun has a mass of 2kg and the bullet has a mass of 10g what speed does the bullet come out at?

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Force and momentumForce and momentumNewton’s second law of motion says that the force acting on an object is that object’s rate of change of momentum. In other words…

mv

TF

Force = Change in momentum Time(in N)

(in kgm/s)(in s)

For example, David Beckham takes a free kick by kicking a stationary football with a force of 40N. If the ball has a mass of 0.5kg and his foot is in contact with the ball for 0.1s calculate:

1) The change in momentum of the ball (its impulse),2) The speed the ball moves away with

Also called “impulse”

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Example questionsExample questions1) Ben likes playing golf. He strikes a golf ball with a

force of 80N. If the ball has a mass of 200g and the club is in contact with it for 0.2s calculate a) the change in momentum of the golf ball, b) its speed.

2) Nick thinks it’s funny to hit tennis balls at Tom. He strikes a serve with a force of 30N. If the ball has a mass of 250g and the racket is in contact with it for 0.15s calculate the ball’s change in momentum and its speed.

3) Dan takes a dropkick by kicking a 0.4kg rugby ball away at 10m/s. If his foot was in contact with the ball for 0.1 seconds calculate the force he applied to the ball.

4) Simon strikes a 200g golf ball away at 50m/s. If he applied a force of 50N calculate how long his club was in contact with the ball for.

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Safety featuresSafety featuresLet’s use Newton’s Second Law to explain how airbags work:

mv

TF

Basically:1) The change in momentum is the same with or without

an airbag2) But having an airbag increases the time of the collision3) Therefore the force is reduced

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Static ElectricityStatic ElectricityStatic electricity is when charge “builds up” on an object and then stays “static”. How the charge builds up depends on what materials are used:

+ -

+-

+

+-

--+

++

-

-

++

+-

--

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Static ElectricityStatic Electricity

+++ ---

------

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Van de Graaf generatorsVan de Graaf generators

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Uses of Static – Smoke PrecipitatorsUses of Static – Smoke Precipitators

---

---

+ ++

Chimney

Negatively charged

plates

Positively charged

grid

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Uses and dangers of Static Uses and dangers of Static ElectricityElectricity

Find out how static electricity is used in the following:

1) Photocopiers2) Paint sprayer

Find out how static electricity is dangerous in the following situations:

1) Fuel pipes2) Hospitals

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Circuit SymbolsCircuit Symbols

VA

Battery

CellFuse

ResistorLDR

VoltmeterAmmeter

Variable resistorDiodeSwitchBulb

Thermistor

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Electric CurrentElectric CurrentElectric current is a flow of negatively charged particles (i.e. electrons).

Note that electrons go from negative to positive-+ e-

e-

By definition, current is “the rate of flow of

charge”

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Basic ideas…Basic ideas…Electric current is when electrons start to flow around a circuit. We use an _________ to measure it and it is measured in ____.

Potential difference (also called _______) is how big the push on the electrons is. We use a ________ to measure it and it is measured in ______, a unit named after Volta.Resistance is anything that resists an electric current. It is measured in _____.

Words: volts, amps, ohms, voltage, ammeter, voltmeter

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More basic ideas…More basic ideas…If a battery is added the current will ________ because there is a greater _____ on the electrons

If a bulb is added the current will _______ because there is greater ________ in the circuit

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Current in a series circuitCurrent in a series circuitIf the current here is 2 amps…

The current here will be…

The current here will be…

And the current here will be…

In other words, the current in a series circuit is THE SAME at any

point

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Current in a parallel circuitCurrent in a parallel circuitA PARALLEL circuit is one where the current has a “choice of routes”

Here comes the current…

And the rest will go down here…

Half of the current will go down here (assuming the bulbs are the same)…

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Current in a parallel circuitCurrent in a parallel circuit

If the current here is 6 amps

The current here will be…

The current here will be…

The current here will be…

And the current here will be…

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Some example questions…Some example questions…

3A6A

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Voltage in a series circuitVoltage in a series circuit

V

V V

If the voltage across the battery is 6V…

…and these bulbs are all identical…

…what will the voltage across each bulb be? 2V

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Voltage in a series circuitVoltage in a series circuit

V

V

If the voltage across the battery is 6V…

…what will the voltage across two bulbs be?

4V

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Voltage in a parallel circuitVoltage in a parallel circuit

If the voltage across the batteries is 4V…

What is the voltage here?

And here?

V

V4V

4V

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SummarySummaryIn a SERIES circuit:

Current is THE SAME at any point

Voltage SPLITS UP over each component

In a PARALLEL circuit:

Current SPLITS UP down each “strand”

Voltage is THE SAME across each”strand”

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An example question:An example question:

V1

V2

6V3A

A1

A2

V3

A3

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Another example question:Another example question:

V1

V2

10V3A

A1

A2

V3

A3

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Georg Simon Ohm 1789-1854

ResistanceResistance

Resistance is anything that will RESIST a current. It is

measured in Ohms, a unit named after me.

The resistance of a component can be calculated using Ohm’s Law:

Resistance = Voltage (in V) (in ) Current (in A)

V

RI

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An example question:An example question:

V

A

1) What is the resistance across this bulb?

2) Assuming all the bulbs are the same what is the total resistance in this circuit?

Voltmeter reads 10V

Ammeter reads 2A

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More examples…More examples…

12V

3A

3A

6V

4V

2A

1A2V

What is the resistance of these bulbs?

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ResistanceResistance

Resistance is anything that opposes an electric current.Resistance (Ohms, ) = Potential Difference (volts, V)

Current (amps, A)What is the resistance of the following:1) A bulb with a voltage of 3V and a current of 1A.2) A resistor with a voltage of 12V and a current of

3A3) A diode with a voltage of 240V and a current of

40A4) A thermistor with a current of 0.5A and a voltage

of 10V

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Resistors, bulbs and diodesResistors, bulbs and diodes

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Current-Voltage GraphsCurrent-Voltage Graphs

Voltage on powerpack/V

Current/A Voltage/V

1210…0…-10-12

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Current-voltage graphsCurrent-voltage graphsI

VI

V

I

V

1. Resistor 3. Diode

2. BulbCurrent increases in proportion to voltage

As voltage increases the bulb gets hotter and resistance increases

A diode only lets current go in one direction – it has very high resistance in the other direction

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LDRs and ThermistorsLDRs and Thermistors

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Two simple components:Two simple components:2) Thermistor – resistance DECREASES when temperature INCREASES

1) Light dependant resistor – resistance DECREASES when light intensity INCREASES

Resistance

Amount of light

Resistance

Temperature

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Wiring a plugWiring a plug

Earth wire

Neutral wire

Insulation

Live wire

Fuse

1.

2.

3.

4.

5.

6. Cable grip

The live wire of a plug alternates between positive and

negative potential relative to the Earth

The neutral wire of a plug stays at a potential close to zero

relative to the Earth

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DC and ACDC and AC

DC stands for “Direct Current” – the current only flows in one direction:

AC stands for “Alternating Current” – the current changes direction 50 times every second (frequency = 50Hz)

1/50th s

230V

V

V

Time

T

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Using an oscilloscopeUsing an oscilloscopeQ. What is the voltage and frequency of this supply?

This number tells you how many seconds each square on the horizontal axis

represents

This number tells you how many

volts each square on the vertical axis represents

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FusesFusesFuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____.

Words – large, harm, safety, melt, live, circuit, fuse

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Power and fusesPower and fuses

Power is “the rate of doing work”. The amount of power being used in an electrical circuit is given by:

P

IVPower = voltage x current in W in V in A

Using this equation we can work out the fuse rating for any appliance. For example, a 3kW (3000W) fire plugged into a 240V supply would need a current of _______ A, so a _______ amp fuse would be used (fuse values are usually 3, 5 or 13A).

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Power and fusesPower and fusesCopy and complete the following table:

Appliance Power rating (W)

Voltage (V) Current needed (A)

Fuse needed (3, 5

or 13A)Toaster 960 240

Fire 2000 240

Hairdryer 300 240

Hoover 1000 240

Computer 100 240

Stereo 80 240

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Energy and PowerEnergy and PowerThe POWER RATING of an appliance is simply how much energy it uses every second.

In other words, 1 Watt = 1 Joule per second

E

TP

E = Energy (in joules)

P = Power (in watts)

T = Time (in seconds)

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Some example questionsSome example questions1) What is the power rating of a light bulb that transfers

120 joules of energy in 2 seconds?2) What is the power of an electric fire that transfers

10,000J of energy in 5 seconds?3) Farhun runs up the stairs in 5 seconds. If he transfers

1,000,000J of energy in this time what is his power rating?

4) How much energy does a 150W light bulb transfer in a) one second, b) one minute?

5) Shaun’s brain needs energy supplied to it at a rate of 40W. How much energy does it need during a physics lesson?

6) Damien’s brain, being more intelligent, only needs energy at a rate of about 20W. How much energy would his brain use in a normal day?

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Earth wiresEarth wiresEarth wires are always used if an appliance has a _____ case. If there is a _____ in the appliance, causing the live wire to ______ the case, the current “_______” down the earth wire and the ______ blows.

Words – fuse, fault, metal, surges, touch

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Charge (Q)Charge (Q)As we said, electricity is when electrons move around a circuit and carry energy with them. Each electron has a negative CHARGE. Charge is measured in Coulombs (C). We can work out how much charge flows in a circuit using the equation:

Q

TI

Charge = current x time(in C) (in A) (in s)

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Example questionsExample questionsCharge (C) Current (A) Time (s)

5 20.4 120 0.550 250

3 60

1) A circuit is switched on for 30s with a current of 3A. How much charge flowed?

2) During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for?

3) A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed?

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Energy and chargeEnergy and charge

The amount of energy that flows in a circuit will depend on the amount of charge carried by the electrons and the voltage pushing the charge around:

E

QV

Energy transferred = charge x voltage

(in J) (in C) (in V)

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Example questionsExample questions1) In a radio circuit a voltage of 6V is applied and a

charge of 100C flows. How much energy has been transferred?

2) In this circuit the radio drew a current of 0.5A. How long was it on for?

3) A motor operates at 6V and draws a current of 3A. The motor is used for 5 minutes. Calculate: a) The motor’s resistance, b) the charge flowing through it, c) the energy supplied to it

4) A lamp is attached to a 12V circuit and a charge of 1200C flows through it. If the lamp is on for 10 minutes calculate a) the current, b) the resistance, c) the energy supplied to the bulb.

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Random questionsRandom questions1) A battery has a voltage of 12V and it puts a current of

3A through a bulb. What is the bulb’s resistance?2) Another bulb transfers 120C of charge in 2 minutes.

What was the current through it?3) A powerpack transfers 2,000J to a motor. If the motor

ran on a voltage of 50V how much charge was transferred?

4) A hairdryer runs on a 50Hz power supply. If it has a power rating of 200W what fuse should it have?

5) An electric fire transfers 3MJ of energy. If it has a power rating of 2KW calculate how long it was on for, the current it ran on (assuming it was connected to the mains supply) and the amount of charge it transferred.

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Structure of the atomStructure of the atom

A hundred years ago people thought that the atom looked like a “plum pudding” – a sphere of positive charge with negatively charged electrons spread through it…

I did an experiment (with my colleagues Geiger and Marsden)

that proved this idea was wrong. I called it the “Scattering

Experiment”

Ernest Rutherford, British scientist:

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The Rutherford Scattering ExperimentThe Rutherford Scattering Experiment

Alpha particles (positive

charge, part of helium

atom)

Thin gold foil

Most particles passed through, 1/8000 were

deflected by more than 900

Conclusion – atom is made up of a small, positively charged nucleus surrounded by

electrons orbiting in a “cloud”.

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The structure of the atomThe structure of the atomELECTRON –

negative, mass nearly

nothing

PROTON – positive,

same mass as neutron

(“1”)

NEUTRON – neutral,

same mass as proton

(“1”)

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The structure of the atomThe structure of the atomParticle Relative Mass Relative

ChargeProton 1 +1

Neutron 1 0Electron 0 -1

MASS NUMBER = number of protons + number of neutrons

SYMBOL

PROTON NUMBER = number of protons (obviously)

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IsotopesIsotopesAn isotope is an atom with a different number of neutrons:

Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.

Notice that the mass number is different. How many neutrons does each isotope have?

A “radioisotope” is simply an isotope that is radioactive – e.g. carbon 14, which is used in carbon dating.

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Background RadiationBackground Radiation

Radon gasFoodCosmic raysGamma raysMedicalNuclear power

13% are man-made

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Types of radiationTypes of radiation1) Alpha () – an atom decays into a new atom and emits an alpha particle (2 protons and 2 ______ – the nucleus of a ______ atom)

2) Beta () – an atom decays into a new atom by changing a neutron into a _______ and electron. The fast moving, high energy electron is called a _____ particle.

3) Gamma – after or decay surplus ______ is sometimes emitted. This is called gamma radiation and has a very high ______ with short wavelength. The atom is not changed.

Unstable nucleus

Unstable nucleus

Unstable nucleus

New nucleus

New nucleus

New nucleus

Alpha particle

Beta particle

Gamma radiation

Words – frequency, proton, energy, neutrons, helium, beta

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Nuclear fissionNuclear fission

Uranium or

plutonium nucleus

Unstable

nucleus New nuclei (e.g. barium

and krypton)

More neutron

s

Neutron

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Chain reactionsChain reactions

Each fission reaction releases neutrons that are used in further reactions.

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Nuclear Fusion in starsNuclear Fusion in starsProton Neutron