Electromagnetic Induction — A/L Physics

What must I remember about Electromagnetic Induction?

• Magnetic Flux (Φ): Measure of magnetic field lines penetrating surface area A: Φ = B · A = B A cos θ (units Weber = T·m² = V·s).
• Faraday's Law of Electromagnetic Induction: The magnitude of induced electromotive force in a circuit is directly proportional to the time rate of change of magnetic flux linkage through the circuit: E = - d(N Φ)/dt.
• Lenz's Law: The direction of induced EMF (and induced current) is always such that its magnetic effects oppose the very change in magnetic flux that produced it (accounted for by the negative sign in Faraday's law; direct consequence of Conservation of Energy).
• Motional EMF: A conducting rod of length L translating with velocity v perpendicular to uniform magnetic field B develops motional emf between its ends: E = B L v; direction of induced current given by Fleming's Right-Hand Rule.

Test yourself (1 minute)

1. Eddy Currents

   Closed circulating loops of induced current generated inside solid conducting masses subjected to varying magnetic fields; generate unwanted Joule heating (I²R loss); minimized by laminating cores into insulated sheets (transformers) or utilized constructively in induction cookers and electromagnetic braking.

2. Self-Inductance (L) and Mutual Inductance (M)

   Self-induced emf E = - L (dI/dt); Mutual induced emf E2 = - M (dI1/dt); Inductance of solenoid L = μ0 n² A L; Energy stored in inductor U = (1/2) L I².

3. Rotating Coil in Magnetic Field (AC Generator)

   Coil of N turns and area A rotating at angular velocity ω: Instantaneous flux Φ = B A cos(ωt); Induced emf E = - dΦ/dt = E0 sin(ωt) where peak emf E0 = N B A ω.

Practise Electromagnetic Induction questions today

Source: NIE G.C.E. (A/L) Physics Resource Book - Unit 8: Electromagnetism

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Next in the syllabus

Where does Electromagnetic Induction fit in the syllabus?

Unit 8.3 · Year 2 · Term 1