(a) State the laws of electromagnetic induction. (b) Draw a labelled diagram of a simple d.c. generator and explain how it works. (c) State three methods by...

(a) Laws of electromagnetic induction

1. Whenever the magnetic flux linking a conductor or coil changes, an e.m.f. is induced in it. The magnitude of the induced e.m.f. is proportional to the rate of change of flux linkage:
   \[E=-N\frac{d\Phi}{dt}.\]
2. The induced current flows in such a direction as to oppose the change in magnetic flux that produces it. This is Lenz's law.

(b) Labelled diagram of a simple d.c. generator

How it works: A rectangular coil is rotated mechanically between the poles of a magnet. As the coil rotates, the magnetic flux linking it changes and an e.m.f. is induced in the coil. The induced e.m.f. in the coil reverses after every half revolution. However, at the same instant, the split-ring commutator reverses contact with the carbon brushes. Thus, the connections to the external circuit are reversed whenever the coil current reverses, so current in the external circuit always flows in one direction. The output is therefore a pulsating direct current.

(c) Three methods of obtaining a higher e.m.f.

1. Increase the number of turns of wire in the coil.
2. Use a stronger magnetic field, for example by using stronger magnets or a soft-iron core.
3. Rotate the coil faster.