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Edexcel ScienceiGCSE Physics

W. Electromagnetic Induction2019-2020

Name:________________Physics Teacher:______________

House CG

Year 11

Specification Checklist

6.01 use the following units: ampere (A), volt (V) and watt (W)

6.02 know that magnets repel and attract other magnets and attract magnetic substances

6.04 understand the term magnetic field line

6.07 describe how to use two permanent magnets to produce a uniform magnetic field pattern

6.10 draw magnetic field patterns for a straight wire, a flat circular coil and a solenoid when each is carrying a current

6.15 know that a voltage is induced in a conductor or a coil when it moves through a magnetic

field or when a magnetic field changes through it and describe the factors that affect the

size of the induced voltage

6.16 describe the generation of electricity by the rotation of a magnet within a coil of wire and of

a coil of wire within a magnetic field, and describe the factors that affect the size of the

induced voltage

6.17 describe the structure of a transformer, and understand that a transformer changes the size of an alternating voltage by having different numbers of turns on the input and output sides

6.18 explain the use of step-up and step-down transformers in the large-scale generation and transmission of electrical energy

6.19 know and use the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer:

input ( primary ) voltageoutput (secondary ) voltage

= primary turnssecondary turns

6.20 know and use the relationship: input power = output power V p I p=V s I zfor 100% efficiency

Electromagnetic Induction – Science (Physics) 2

Key Word

Image Definition

Alternating Current (a.c.)

Current that repeatedly changes direction. This is what comes out of your plug socket.

Efficiency Efficiency is a measure of how much work or energy is conserved in a process

Electromagnet A soft iron core wrapped in wire. When current flows through the coil it becomes magnetic.

Field Line An indication of the strength and direction of the magnetic field. The denser the lines the stronger the field.

Generator A machine that converts one form of energy into another, especially mechanical energy into electrical energy

Induction The induction of voltage by the motion of a conductor across a magnetic field

Iron Core The centre of an electromagnet. It boosts the power of a solenoid.

Left Hand Rule (Motor Effect)

The relationship between magnetic field direction, electrical current in a wire and the force on the wire while inside a magnetic field.

Magnetic Field An area where other magnetic objects experience a force of attraction and repulsion.

National Grid The national grid system is the network of cables and transformers which transport electricity from the power stations in Britain to homes, factories and other places that require it

Step-down transformer

A transformer that changes a high-voltage supply into a low-voltage one

Step-up Transformer

A transformer that changes a low-voltage supply into a high-voltage one


Key Words

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjg9L6h1MzfAhXFyYUKHeHtCcAQjRx6BAgBEAU&url=http://www.frankswebspace.org.uk/ScienceAndMaths/physics/physicsGCSE/efficiency.htm&psig=AOvVaw0bg9srUOau8HccYJrLgNCo&ust=1546434679285347

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjo5eiI1MzfAhUQyIUKHdBbB24QjRx6BAgBEAU&url=http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motorac.html&psig=AOvVaw1zRraJ3gln2mIjAZ6XIrUl&ust=1546434616197008

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjBsOj108zfAhVFxIUKHXBeAQAQjRx6BAgBEAU&url=https://tap.iop.org/fields/electromagnetism/414/page_46948.html&psig=AOvVaw1280Z8K_owbIF_8lfI-fdu&ust=1546434585429170

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjzxJLm08zfAhUNvxoKHXkaCHAQjRx6BAgBEAU&url=https://www.cyberphysics.co.uk/topics/magnetsm/electro/nat_grid.htm&psig=AOvVaw3Cv7VWl3017cnKhIKTtZUU&ust=1546434552755700

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwig9YvJ08zfAhVDvxoKHVChD_0QjRx6BAgBEAU&url=http://www.learningaboutelectronics.com/Articles/What-is-a-step-down-transformer&psig=AOvVaw3WeQDn5rbpa1O8TwCviOfh&ust=1546434493792475

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwiL14rW08zfAhVC6RoKHWvsDhoQjRx6BAgBEAU&url=http://www.learningaboutelectronics.com/Articles/What-is-a-step-up-transformer&psig=AOvVaw0_tFxtS_5ZrS9xlliQwZef&ust=1546434520925655

1: Inducing Voltage

Knowledge and Understanding Recap QuizUse the knowledge you have gained since Shell to answer the following questions

1. What is the efficiency of a light bulb that gives out 120J of light energy when supplied with 300J of electrical energy?

……………… (3)

2. What is Hooke’s Law?

…………………………………………………………………………………………………………………………………………………………………………………… (2)

3. What is the definition of a transverse wave?

…………………………………………………………………………………………

………………………………………………………………………………………… (2)

4. What are the units of power?

…………………………………………………………………………………………

………………………………………………………………………………………… (1)

5. Sketch the magnetic field shape and direction around the wire below.

(2)

6. What is the name given to a collection of billions of stars?

…………………………………………………………………………………………

………………………………………………………………………………………… (1)

Score [ /11]


Learning Outcomes:

1. Describe how to induce voltage in a conducting wire. 2. Investigate the factors which affect the size of this induced voltage. 3. Explain why these factors result in a larger induced voltage.

Inducing Voltage in a Wire

Key Ideas

1. A voltage can be induced if we move a conductor (e.g. a wire) at 90o (right angles) to a magnetic field.

2. This occurs because the conductor cuts through the magnetic field lines. 3. We can say that the voltage is induced or generated in the wire. 4. This voltage may cause a current to flow in the wire (if we have a complete circuit)5. The direction of this current depends on:

a. The direction of the magnetic field


b. The direction of the force (movement) on the wire.

W1: Inducing Voltage in a Wire

In this investigation you are going to investigate what factors affect the size of the induced voltage in a wire.

In this investigation the method is written in the questions and will be underlined so it is vital that you work methodically through these.

W1: Method and questions

1. In this investigation, what is important about the direction of motion and the direction of the magnetic field in relation to each other?

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2. Set up a yoke with two magnets with opposite poles facing each other.

Connect a length of insulating wire to a sensitive ammeter or voltmeter.

Move the wire down between the poles of the magnet

Describe your observations as specifically as you can.

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3. Move the wire up between the poles of the magnet

Describe your observations as specifically as you can.

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4. Try to move the wire in such a way that you get the biggest induced voltage or current that

you can.

How did you make the induced voltage bigger?

……………………………………………………………………………………………………….


Health and Safety Check!

Keep any strong magnetsaway from electronicdevices.

North

-+

5. Add an extra magnet to each end of the yoke.

Move the wire up and down through the magnetic field again.

How do your results compare to your results in parts 2 and 3?

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6. There is one more way to increase the induced voltage in the wire. Using your knowledge

from the Magnetism and Electromagnetism topic, can you think of a way that you might do

this?

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7. Discuss your ideas with your teacher.

In the space below sketch the set up you would need to increase the induced voltage using

your ideas from part 6.

8. Test your above hypothesis.

What were your results?

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Increasing the Induced Voltage in a Wire

Key Ideas

1. The size of the induced voltage (and current) in a wire can be increased in three ways. 2. These are:

a. Moving the wire more quickly (more field lines are cut in a given time/field lines are cut faster)

b. Using a stronger magnet (there are more magnetic field lines to cut)c. Wrapping the wire into a coil (so that more pieces of wire move through the

magnetic field).


2: Induction in Coils and Generators

Knowledge and Understanding Recap QuizUse the knowledge you have gained since Shell to answer the following questions

1. How long will it take 600C of charge to pass a point in a wire if 8A of current is flowing?

……………… (3)

2. What is Newton’s Third Law?

…………………………………………………………………………………………………………………………………………………………………………………… (2)

3. What is -60oC in K?

…………………………………………………………………………………………

………………………………………………………………………………………… (1)

4. What is the order of the EM spectrum from highest to lowest frequency?

(2)

5. Which type of radiation is the most ionising?

…………………………………………………………………………………………

………………………………………………………………………………………… (1)

6. Sketch the magnetic field shape and direction around the bar magnet below:

(3)

Score [ /12]


Learning Outcomes:

1. Describe how a voltage can be induced in a coil of wire using a magnet2. Explain what changes can be made to increase the size of this induced voltage3. Explain how a generator can be used to turn kinetic energy into electrical energy

Inducing Voltage in a Coil

Key Ideas

1. You can also induce/generate a voltage by pushing/dropping a magnet into a coil of conducting wire.

2. The magnet (or coil) must be moving for a voltage to be induced.3. Just like before the coil is cutting the magnetic field lines of the magnet to generate the

voltage.


https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwiVjJPZ38zfAhVLQhoKHblPCV8QjRx6BAgBEAU&url=https://www.ck12.org/physics/electromagnetic-induction/lesson/Electromagnetic-Induction-MS-PS/&psig=AOvVaw0gWKRDtoE6jEDsFL-7gbAl&ust=1546437737974831

W2: Inducing Voltage in a Coil

In this investigation you are going to investigate what factors affect the size of the induced voltage in a coil.

In this investigation the method is written in the questions and will be underlined so it is vital that you work methodically through these.

W2: Method and questions

1. Connect your coil to a sensitive ammeter or voltmeter using leads.

Move the magnet and coil respectively to complete to table

[Note: if using a digital ammeter, indicate the direction of needle as + or – (as it appears on

the digital display].

Moving Component

South pole towards magnet

North pole towards magnet

Direction of Ammeter Needle [left or right]

Magnet into coil

Magnet out of coil

Coil towards magnet

Coil away from magnet

Coil and magnet moved up

and down together



Keep any strong magnetsaway from electronicdevices.

Ammeter or Voltmeter

2. What can you conclude from these results?

Hint: Consider the relative direction of magnet and coil.

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3. Try to move the magnet in such a way that you get the biggest induced voltage or current

that you can.

How did you make the induced voltage bigger?

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4. Replace your coil for one with more turns.

Move the magnet through the coil again.

How do your results compare to part 1?

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5. There is one more way to increase the induced voltage in the coil. Using your knowledge

from the Magnetism and Electromagnetism topic, can you think of a way that you might do

this?

……………………………………………………………………………………………………….

……………………………………………………………………………………………………….

6. Test your above hypothesis.

What were your results?

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Summarise below the 3 ways to increase the induced voltage in a coil:

1. …………………………………………………………………………………………………………

2. …………………………………………………………………………………………………………


3. …………………………………………………………………………………………………………

Generators

Key Ideas

1. The coil (or magnet) is rotated within a magnetic field (or coil)2. As it turns the coil cuts the magnetic field lines. 3. This induces a voltage (or current) in the coil. 4. The coil can then be connected to an existing circuit. 5. In a generator, energy is being converted from kinetic (mechanical) energy into

electrical energy. 6. The size of the induced voltage (or current) can be increased by:

a. Using a stronger magnetb. Having more turns in the coilc. Spinning/moving the coil (or magnet) faster.


Model Answer: The Generator

Below is an example of an exam question on generators.

Attempt the question yourself first using the knowledge you have just gained. Make sure you use green pen to add any keyword that you have missed to make sure

you have a model answer.

1. Explain how a generator works. (3)

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2. Explain the effect on the inducted voltage when the following changes are made to a

generator

a. A stronger magnet is used. (2)

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b. The coil rotates fewer times per second. (2)

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What did you miss the first time around?


3. The Transformer

Knowledge and Understanding QuizUse the knowledge you have gained since Shell to answer the following questions

1. A box weighing 550N rests on the floor on a base of area 0.75m2. What pressure is the box putting on the floor?

……………… (3)

2. A light ray hits a boundary between air and glass. On the image below add:a. The normal (1)b. The direction of the refracted ray (by eye) (1)

3. What are the names of the 3 wires in a plug?

…………………………………………………………………………………………

………………………………………………………………………………………… (3)

4. Car X has a mass of 550kg and is travelling at 6m/s when it collides with a stationary car

(Car Y) with a mass of 300kg. If the cars travel together following the collision, how fast

will they be going?

……………… (3)

5. Give two uses for visible light.

…………………………………………………………………………………………

………………………………………………………………………………………… (2)

Score [ /12]


airglass

Learning Outcomes:

1. Describe how a transformer works.2. Explain the difference between a step-up and step-down transformer.

3. Calculate output voltage using the relationship:V p

V s=n pns

How a Transformer Works

Key Ideas

1. Two separate coils, input (primary) and output (secondary), of wire are wound onto a soft iron core.

2. When an a.c. current passes through a coil the direction of the magnetic field around the coil is constantly changing.

3. The changing current in the primary coil produces a changing magnetic field inside the coil, and through the soft iron core.

4. This changing magnetic field cuts through the secondary coil and induces a voltage in it

5. Because a changing magnetic field is needed to induce a voltage, transformers do not work with d.c.

6. There are 2 types of transformer:a. Step-up transformer: increases voltage (decreases current)b. Step-down transformer: decreases voltage (increases current)


https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwijkLiP7MzfAhVCJBoKHV_GAtcQjRx6BAgBEAU&url=http://www.bbc.co.uk/schools/gcsebitesize/science/triple_ocr_gateway/electricity_for_gadgets/transforming/revision/1/&psig=AOvVaw3wxuxW03GoGsupotaOXtBh&ust=1546441034119127

Voltage and Number of Turns

Key Ideas

1. The relationship between the voltages across each of the coils is described by the equation:

input voltageoutput voltage

= number of turns on primary coilnumber of turns onsecondary coil

This equation is sometimes referred to as the ‘turns ratio’2. This can be written:

V p

V s=n pns

3. This equation is given in the exam.

Worked Examples

1. A transformer has 100 turns on its primary coil and 500 turns on its secondary coil. If an alternating voltage of 2V is applied across the primary coil, what is the voltage across the secondary coil?

2. A transformer has 200 turns in its primary coil and is supplied with an input voltage of 50V a.c. How many turns would be needed on the secondary coil to reduce the output voltage to 5V?


Worksheet – The Transformer

Complete the questions below using the equation you have just learnt. You must show all of your working [equation, substitution, solution and units]

1. For each of the 4 transformers below, calculate the output voltage.

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2. A primary coil in a transformer has an input voltage of 240V a.c. and number of revolutions 500 turns. What is the output voltage if the secondary coil has 25 turns?

…………………..

3. A transformer produces an output voltage of 24V. There are 1500 turns on the primary coil and 250 turns on the secondary coil. What must the input voltage have been?

…………………..

4. A transformer has a primary coil with 48 000 turns and the secondary coil with 4000 turns. If the input voltage is 240 V a.c., calculate the output voltage.

…………………..

5. A step down transformer reduces an input of 5000V a.c. to 250V a.c. If there are 2000 turns in the primary coil, how many turns must there be in the secondary coil?

…………………..

6. Calculate the number of secondary turns needed if a 3V lamp is to be correctly lit using a 24 V a.c. supply and a transformer with 480 turns on the primary coil.

…………………..


W3: Building a Transformer

In this investigation you are going to build a transformer and use it to test the equation you have just learnt.

What is the equation that describes the relationship betweenthe input/out voltage and the number of turns on the primaryand secondary coil?

In the space below sketch and label a step-down transformer.

Method

1. Set up your transformer as per your sketch. 2. Ensure that your primary coil has 120 turns (np) and is connected to an input voltage

of 6V a.c. (Vp) Note: A voltmeter will need to be connected across your power supply to take the actual input voltage (it will be less than 6).

3. Now wrap a length of insulated wire to create a secondary coil with 20 turns (ns). 4. Connect a voltmeter across the secondary coil. 5. Switch on your power supply and note the output voltage in your table (Vs). 6. Repeat steps 3-5 for different values of ns.

7. Use a calculator to calculate the values for the 3rd and 6th column of your results table.



Coils can get hot duringuse. Handle with care and do not leave on for longperiods of time.

Results

Input Voltage Vp

[V]

Output Voltage Vs

[V]

V p

V s

Primary Turns np

Secondary Turns

ns

npns

120 20

120 18

120 16

120 14

120 12

120 10

120 8

120 6

120 4

120 2

What do you notice about the values in the shaded columns of your table?

……………………………………………………………………………………………………………….……………………………………………………………………………………………………………….

What would have happened if we had used a d.c. input instead of an a.c. input?

……………………………………………………………………………………………………………….……………………………………………………………………………………………………………….

How would you expect your results to change if you had built a step-up transformer instead?

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4. Efficiency and Transmitting Electricity

Knowledge and Understanding QuizUse the knowledge you have gained since Shell to answer the following questions

1. Sketch the shape of the magnetic field around the solenoid below.

(2)

2. Name two types of renewable energy resource.

…………………………………………………………………………………………

………………………………………………………………………………………… (2)

3. A transformer has 500 turns on the primary coil and 75 turns on the secondary coil. If

the input voltage is 150V a.c. what would we expect the output voltage to be?

……………… (3)

4. Sketch the I-V graph for a light bulb.

(3)

5. What is the name given to the phenomena which causes the observed wavelength of a

wave to change as it moves past an observer?

…………………………………………………………………………………………

………………………………………………………………………………………… (1)

Score [ /11]


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Learning Outcomes:

1. Identify the importance of having an efficient transformer.2. When a transformer is 100% efficient use the equation:

I pV p=I sV s

3. Explain the importance of transformers in the National Grid with reference to current and energy loss.

Energy and Efficiency in Transformers

Key Ideas

1. It is important to try and make transformers as efficient as possible so that energy is not wasted.

2. If a transformer is 100% efficient, then the electrical energy entering the primary coil will be equal to the electrical energy leaving the secondary coil. 3. Another way of saying this is that the input power is equal to the output power.

This can be written:I pV p=I sV s

4. This equation is not given in the exam.

Worked Examples

1. A voltage of 12V a.c. is applied across the primary coil of a step-down transformer. There is a current of 0.4A in the primary coil. Calculate the current in the secondary coil if the voltage induced across it is 2V a.c.

2. A current of 0.2 A is supplied to the primary coil of a transformer with an input voltage of 230V a.c. The secondary coil has a 4.0 A current flowing through it. Calculate the output voltage across the secondary coil.


Worksheet – The Efficient Transformer

Complete the questions below using the equation you have just learnt. You must show all of your working [equation, substitution, solution and units]

In each of the questions below, assume the transformer is 100% efficient.

1. A voltage of 650V a.c. is applied across the primary coil of a step-down transformer. There is a current of 5A in the primary coil. Calculate the current in the secondary coil if the voltage induced across it is 15V a.c.

…………………..

2. A current of 2.4 A is supplied to the primary coil of a transformer with an input voltage of 100V a.c. The secondary coil has a 52 A current flowing through it. Calculate the output voltage across the secondary coil.

…………………..

3. A transformer is supplied with a input voltage of 320V. The output voltage at the secondary coil is 125V and it produces a current of 6A. What must the current be through the primary coil?

…………………..

4. A voltage of 2.5kV a.c. is applied across the primary coil of a step-down transformer. There is a current of 0.2A in the primary coil. Calculate the current in the secondary coil if the voltage induced across it is 500V a.c.

…………………..

The National Grid


Key Ideas

1. The National Grid is a network of wires and cables that carries electrical energy from power stations to consumers across the UK.

2. Due to their long length, these wires and cables can lose a lot of energy (waste) in the form of heat.

3. The larger the current in the wire, the more energy is lost as heat. 4. To reduce the amount of energy lost as heat we need to make the current in the wires

as small as possible. 5. Transformers do this by increasing the voltage across the wires and cables. 6. This means that electricity is transmitted through the National Grid at low currents and

high voltages. 7. Transformers are used before electricity is transmitted into homes to decrease the

voltage to the mains value of 230V.


https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwi7wfzv_czfAhULUhoKHYcdDKcQjRx6BAgBEAU&url=https://www.cyberphysics.co.uk/Q&A/KS4/magnetism/transformer/A4.html&psig=AOvVaw3wVv3-To7PP194Qmy3vY4I&ust=1546445813661901

Worksheet – Electromagnetic Induction


Stretch Activity – Michael Faraday

Michael Faraday was the first person to observe how the size of an induced voltage depended upon the rate at which magnetic lines were cut.

But this was not all that he did! Use your laptop to research Michael Faraday and his contribution to Physics.

Note your findings below.

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Stretch Activity – Bicycles and Generating Electricity

Charities and companies all over the UK (e.g. WWF) run fundraising events to raise awareness on environmental issues. Many of these take the form of cycling events where participants take turns riding specially designed stationary bikes. These bikes are fitted with special devices which turn kinetic energy into electrical energy!

https://www.wwf.org.uk/events/cycling

Use your laptop to research answers to the following questions.

How do these bikes work? How much electrical energy can one person generate on the bike in 1 hour? Could this be a feasible way to generate energy globally?

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https://www.wwf.org.uk/events/cycling

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Electromagnetic Induction

Past Paper Questions

Q1. Photograph E shows a rechargeable torch.


(a) When a student shakes the torch, the magnet moves through the coil and back again.This induces a voltage across the ends of the coil.The voltage is used to provide current to recharge the battery.

(i) Explain why a voltage is induced.

(2)

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(ii) State one way to increase this voltage.

(1)

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(b) Photograph F shows the components inside the torch.


The torch uses a light-emitting diode (LED) to provide light.(i) When the LED is on, it shows that

(1)

A the current is alternating

B the torch is switched off

C there is a current in the circuit

D there is a fault in the circuit

(ii) The manufacturer of the torch states, "An LED is a more efficient source of light

than a filament lamp."

Explain this statement in terms of energy transfer.

(2)

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(Total for question = 6 marks)


Q2.

The diagram shows a magnet held above a coil. The coil is connected to a voltmeter.

(a) The magnet is released and falls into the coil.(i) Explain why the voltmeter shows a reading.

(2)

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(ii) The magnet is released from a greater height.

How does this affect the voltmeter?

Explain your answer.

(2)

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(b) State how the voltmeter reading changes when the same magnet(i) moves more slowly into the coil

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(ii) moves into a coil with more turns(1)

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(iii) is reversed so that the S-pole enters the coil first.(1)

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Q3.

Some students are investigating a simple electric motor.

(a) When the switch is closed the coil spins on the axle.State why.

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(b) State two changes that would make the motor spin faster.

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(c) The students change their circuit, replacing the cell and switch with a lamp.

When they spin the coil by hand, the lamp lights.Explain why the lamp lights.

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Q4. A soldering iron is a tool used when joining electronic components in a circuit.

It has an electric heater.

(a) Soldering iron A operates when connected to the mains supply.

Soldering iron A is labelled 230 V, 30 W.(i) What does 30 W tell you about the energy transfer in the soldering iron?

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(ii) This soldering iron has an earth connection.

Explain how an earth connection protects the user.(2)

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(b) Soldering iron B is connected to a low voltage power supply.

Soldering iron B is labelled 24 V, 70 W.A student says:

(i) Use information from the soldering iron labels to evaluate this statement.(3)

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(ii) There is a step-down transformer in the power supply for soldering iron B.Describe the structure of a step-down transformer.You may draw a labelled diagram to help your answer.

(3)

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Electromagnetic Induction

Spec Point Notes

Magnetism and Electromagnetism Specification Notes

6.01 use the following units: ampere (A), volt (V) and watt (W)


6.02 know that magnets repel and attract other magnets and attract magnetic substances

6.04 understand the term magnetic field line

Around every magnet there is a region of space where we can detect magnetism (where magnetic materials will be affected).

This is called the magnetic field and in a diagram we represent this with magnetic field lines.

The magnetic field lines should always point from north to south.

6.07 describe how to use two permanent magnets to produce a uniform magnetic field

pattern

A uniform magnetic field is comprised of straight, parallel lines which are evenly spaced.

6.10 draw magnetic field patterns for a straight wire, a flat circular coil and a

solenoid when each is carrying a current

6.15 know that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it and describe the factors that affect the size of the induced voltage


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Coil is rotated within a magnetic field As it turns the coil cuts the magnetic field lines. This induces a voltage (or current) in the coil. This can then be connected to an existing circuit. In a generator, energy is being converted from kinetic (mechanical) energy into electrical

energy. The size of the induced voltage (or current) can be increased by:

o Using a stronger magneto Having more turns in the coilo Spinning/moving the coil faster.

6.16 describe the generation of electricity by the rotation of a magnet within a coil of wire and of a coil of wire within a magnetic field, and describe the factors that affect the size of the induced voltage

Magnet is rotated within a coil As it turns the coil cuts the constantly changing magnetic field lines from the magnet. This induces a voltage (or current) in the coil. This can then be connected to an existing circuit. In a generator, energy is being converted from kinetic (mechanical) energy into electrical

energy. The size of the induced voltage (or current) can be increased by:

o Using a stronger magneto Having more turns in the coilo Spinning/moving the magnet faster.

6.17 describe the structure of a transformer, and understand that a transformer changes the size of an alternating voltage by having different


numbers of turns on the input and output sides

AC current in the primary coil produces a changing magnetic field around the primary coil.

The iron core channels the changing field through the secondary coil. The changing magnetic field induces a voltage in the secondary coil.

6.18 explain the use of step-up and step-down transformers in the large-scale generation and transmission of electrical energy

Step Up transformers increase the voltage Step Down transformers decrease the voltage

6.19 know and use the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer:

input ( primary ) voltageoutput (secondary ) voltage

= primary turnssecondary turns


6.20 know and use the relationship:

input power = output power V p I p=V s I p

for 100% efficiency


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