Electromagnetic Induction
Physics: Cambridge International GCSE Supplement, topic 4.11.1
Electromagnetic Induction
A current is a flow of charge. An electromotive force (e.m.f) is needed for a current to flow and the e.m.f drives a current round a circuit. An e.m.f can be induced by in two ways.
Electrical conductor moving in magnetic field
- If a wire (or any electrical conductor) moves near a magnet, it induces an e.m.f in the conductor.
Changing magnetic field through electrical conductor
- A changing magnetic field is a magnetic field with changing strength.
- If there is magnetic field through the middle of a coil of wire, it is ‘linked’ with the coil.
- A changing magnetic field that is linked with a coil of wire induces an e.m.f in that wire.
Induced e.m.f
- An induced e.m.f is generated in a conductor when it moves relative to a magnetic field, so that magnetic field lines are cut by the wire.
- The faster the conductor cuts through the magnetic field lines (greater rate of change of flux), the larger the induced emf.
- This principle underpins electromagnetic induction, used in devices such as generators and transformers.
Test yourself on Electromagnetic Induction
What is a current?
Through which processes can an electromotive force be induced?