Question

11.(b) The diagram above illustrates an a.c. generator. When the coil is rotated, an e.m.f. is induced in the coil.
(i) Explain why an e.m.f. is induced.
(ii) State the purpose of the slip rings.
(iii) Name and state the law used to determine the direction of the induced current.
(iv) State two ways to increase the induced e.m.f.

Accepted Answer

(i) As the coil rotates in the magnetic field, it continuously cuts (changes) the magnetic flux linking it, and by electromagnetic induction this changing flux induces an e.m.f. in the coil.
(ii) The slip rings transfer the alternating induced current from the rotating coil to the external circuit continuously.
(iii) Lenz's Law: the direction of the induced current is always such as to oppose the change in magnetic flux producing it.
(iv) Increase the number of turns on the coil; increase the speed of rotation of the coil (also: increase the area of the coil or use a stronger magnet).

WAEC Physics 2018 Theory — Question 22

Sign up free to unlock