AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER
Induced potential
Magnetism and electromagnetism · Lesson 6 of 8
Warm-up
Answer each one, then check.
1. What does a voltmeter measure?
Potential difference
2. What is a magnetic field?
Region where a force acts on a magnet
3. What is a current?
A flow of charge
4. What is a coil?
Loops of wire
5. What is a conductor?
Allows current to flow
Learning Objectives
1. Describe the generator effect.
2. Describe how a potential difference is induced in a wire or coil by moving a magnet.
3. Explain the direction of the induced current and its effect (Higher).
4. Describe the factors that increase the size of the induced potential difference.
The Generator Effect
The generator effect is when a potential difference is induced across a conductor that moves relative to a magnetic field, or when the magnetic field through a conductor changes. If the conductor is part of a complete circuit, a current is induced.
Nothing is induced if there is no change: a stationary magnet in a stationary coil produces no potential difference.
Inducing a Potential Difference
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No change, no induced potential difference. |
A magnet moving into and out of a coil connected to a meter, showing the induced potential difference changing direction.
What Changes the Induced p.d.
Learn the factors.
|
Change |
Effect on the induced potential difference |
|---|---|
|
Faster movement of the magnet |
Larger |
|
Stronger magnet |
Larger |
|
More turns on the coil |
Larger |
|
Reverse the movement |
Direction of p.d. reverses |
|
Reverse the magnet |
Direction of p.d. reverses |
|
Magnet stationary |
No induced p.d. |
Why Does a Current Flow?
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Explain why a current is produced when a magnet is moved into a coil connected in a circuit. |
1. Magnetic field changes
As the magnet moves in, the field through the coil changes
2. p.d. induced
A potential difference is induced across the coil
3. Complete circuit
The induced p.d. makes a current flow
Answer: A changing field induces a p.d., and a current in a complete circuit.
Direction of the Induced Current
Higher tier.
▸ Its own field. The induced current produces a magnetic field of its own.
▸ Opposes the change. This field opposes the change that produced it.
▸ Energy. You have to do work to push the magnet in.
▸ Conservation. That work is what gets transferred to electrical energy.
Key Terms
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Generator effect The induction of a potential difference across a conductor when the magnetic field changes or the conductor moves in a magnetic field. |
Induced potential difference A p.d. produced by the generator effect. |
|
Induced current A current produced in a complete circuit by an induced p.d. |
Coil Loops of wire. |
|
Flux The magnetic field passing through a coil. |
Galvanometer A sensitive meter that shows small currents. |
Your Task: Magnet in a Coil
12 minutes
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Push a bar magnet into a coil connected to a galvanometer. Record the deflection: slowly, quickly, out, stationary. What do you notice? 1. Keep the coil the same. |
A good answer shows: Faster gives a bigger deflection; out reverses it; stationary gives zero.
Can I...?
☐ State the generator effect.
☐ Say what induces a p.d.
☐ Say when a current flows.
☐ List ways to increase it.
☐ Reverse the direction.
☐ Explain no movement, no p.d.
☐ Explain the opposing field.
☐ Link to energy.
Summary
✓ A changing magnetic field induces a potential difference.
✓ Bigger with faster movement, stronger magnet, more turns.
✓ No movement gives no p.d.
✓ Reversing the movement reverses the p.d.
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EXAM FOCUS State two ways of increasing the potential difference induced in a coil. (2 marks) Faster movement, stronger magnet, more turns. |