Question
An a.c. generator consisting of a coil of 100 turns and crosssectional area of 3 m^{2} is rotating at a constant angular speed of 60 rad s^{–1} in a uniform magnetic field of 0.04 T. The resistance of the coil is 500 . Calculate maximum current drawn from the generator, and power dissipation in the coil. From where does the power come?

518.4 W

611.2 W

500.0 W

None of these
medium
Solution
518.4 W
The maximum emf induced in the coil is given by
.
.
.
The maximum current induced in the coil, which can be drawn from the generator is
.
The power dissipated as heat in the resistance of the coil is
= 518.4 W.
The induced current causes a torque on the coil opposing its rotation (Lenz’s law). An external agent (a rotor) does work to produce a counter torque to make the coil rotate uniformly. This work is the source of power dissipated in the coil.
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