Moving a magnet into or out of a coil of wire induces a current in the wire due to electromagnetic induction. A changing magnetic field induces a voltage in any wire cutting through it, causing a current. The induced voltage and current can be increased by moving the magnet or wire faster, using a stronger magnet, adding more turns to the coil, or using a larger coil area. Generators produce electricity through electromagnetic induction by rotating a coil in a magnetic field. Transformers change the voltage of alternating current by using two coils - a changing magnetic field in one coil induces a voltage in the other.

1. 1. If a magnet is moved into a coil of wire
a current is induced in the wire.
2. If the magnet is moved out of the coil
the direction of the current is reversed
3. A wire, or coil of wire, cutting through
a magnetic field will generate a
voltage. This induced voltage causes a
current to flow through the wire
Electromagnetic InductionElectromagnetic InductionElectromagnetic InductionElectromagnetic Induction

2. Electromagnetic InductionElectromagnetic InductionElectromagnetic InductionElectromagnetic Induction

3. Electromagnetic InductionElectromagnetic InductionElectromagnetic InductionElectromagnetic Induction

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5. Electromagnetic InductionElectromagnetic InductionElectromagnetic InductionElectromagnetic Induction

6. Electromagnetic InductionElectromagnetic InductionElectromagnetic InductionElectromagnetic Induction

7. The size of the induced voltage can be
increased if;
• the wire is moved faster
• the magnet is stronger
• the number of turns on the coil is
increased
• the area of the coil is greater
Increasing the voltageIncreasing the voltageIncreasing the voltageIncreasing the voltage

8. Increasing the voltageIncreasing the voltageIncreasing the voltageIncreasing the voltage

9. Increasing the voltageIncreasing the voltageIncreasing the voltageIncreasing the voltage

10. 1. Electricity is generated by rotating a
coil of wire in a magnetic field or by
rotating a magnet inside a coil of wire.
This is how a generator works
Generators and DynamosGenerators and DynamosGenerators and DynamosGenerators and Dynamos

11. Generating ElectricityGenerating ElectricityGenerating ElectricityGenerating Electricity

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13. DynamoDynamoDynamoDynamo

14. 1. Transformers can be used to change
the voltage of an a.c. supply.
2. A changing magnetic field in the
primary coil induces a voltage in the
secondary coil
3. Transformers only work with
alternating voltage
TransformersTransformersTransformersTransformers

15. TransformersTransformersTransformersTransformers

16. 1. Step-up transformers produce high
voltages so that little energy is lost in
power lines (National Grid)
2. Step-down transformers reduce
voltages before the electricity reaches
our homes
3. Primary voltage/Secondary voltage =
Number of turns on primary/Number of
turns on secondary
Step-up & Step-down TransformersStep-up & Step-down TransformersStep-up & Step-down TransformersStep-up & Step-down Transformers

17. Step-up & Step-down TransformersStep-up & Step-down TransformersStep-up & Step-down TransformersStep-up & Step-down Transformers

18. Step up TransformerStep up TransformerStep up TransformerStep up Transformer

19. Step down TransformerStep down TransformerStep down TransformerStep down Transformer

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