Electromagnetic inductionEdexcel International A Level Physics: Flashcards

What these 12 flashcards ask

What is electromagnetic induction?
State Faraday's law.
State Lenz's law.
Write the equation combining Faraday's and Lenz's laws.
What does the minus sign in ε = −d(NΦ)/dt represent?
Why is no e.m.f. induced when a magnet is held still inside a coil?
Give three ways to increase the e.m.f. when a magnet is moved into a coil.
What happens to the polarity of the e.m.f. when the magnet is pulled out instead of pushed in?
Why does closing a switch in a primary coil induce an e.m.f. in a nearby secondary coil?
Why is no e.m.f. induced in the secondary coil once the primary current is steady?
Why does a soft iron core increase the induced e.m.f.?
What is the unit of flux linkage in base units?

Exam questions on Electromagnetic induction

A bar magnet is pushed into a coil of 400 turns that is connected to a sensitive voltmeter. A student observes the voltmeter reading while moving the magnet.
Explain why an e.m.f. is induced across the coil only while the magnet is moving.2 marks
Two coils are wound on the same soft iron core. The primary coil is connected to a battery through a switch. The secondary coil is connected to a sensitive voltmeter.
The battery is replaced by a low-frequency alternating supply. Explain why a continuous alternating e.m.f. is now induced in the secondary coil.2 marks
A flat coil of 250 turns has an area of 4.0 × 10⁻³ m². The plane of the coil is perpendicular to a uniform magnetic field. The flux density of the field is increased steadily from zero to 0.60 T in a time of 0.20 s.
Calculate the magnitude of the e.m.f. induced in the coil while the flux density is increasing.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).