Question 4
- State Faraday’s Law of electromagnetic induction.
- With the aid of a labeled diagram, describe the principle of operation of an electric bell.
Observation
- (a) Whenever there is relative motion between magnetic flux and coil, an e.m.f. is induced. The ratio of change of the linkage with the coil is proportional to the amount of e.m.f. induced.
- (b)
- (c)When the switch is pushed or closed, the circuit is completed and current flows through the electromagnetic coil. Consequently, the iron striker is attracted to the electromagnet and strikes the bell. As the striker moves towards the bell, the contact is broken so that current stops flowing through the coil which consequently loses magnetism. The compressed spring is released and returns the striker to its original position which makes new contact and so electricity flows again. This cycle is repeated for as long as the switch is closed.
