Question

3. A circular coil of wire is rotating in a magnetic field such that it cuts through the field's lines. The amplitude of the induced EMF generated in the coil is 7.9 mV. Which of the following could be done to INCREASE the amplitude of the EMF induced in the coil?

a. reshape the coil into a square instead of a circle

b. rotate the coil such that its axis of rotation is parallel to the magnetic field instead of cutting through it

c. decrease the strength of the field

d. increase the rate of rotation of the coil

Answer 1

The answer is : d.increase the rate of rotation of coil.

When the rate of rotation of coil is increased, the wire will cut the lines of flux at a faster rate.So more induced emf would be produced.

When the coil is reshaped into a square instead of a circle, then the area through which the magnetic field lines passing is decreased.So the emf induced also decreases.(For a circle and square having same perimeter,the area will be more for a circle).

If we rotate the coil such that its axis of rotation is parallel to magnetic field, then there will be no flux lines passing through the area enclosed by the coil.So emf will not be induced.Emf will only be induced if the magnetic flux lines pass through the area encloed.

If we decrease the strength of the field, there will be less number of field lines to cut.So the emf induced will also decreases.