Question

A 60.0-Hz generator delivers an average power of 75 W to a single light bulb. When an induced current exists in the rotating coil of a generator, a torque—called a countertorque—is exerted on the coil. Determine the maximum countertorque in the generator coil. (Hint: The peak current, peak emf, and maximum countertorque all occur at the same instant.) Answer: 0.4 Nm

Answer 1

Given:

   Frequency of the generator = f = 60.0 Hz

   thus, Angular velocity of the generator

   W = 2 π f = 2(3.14)(60.0) = 376.99 rad/s

Average Power delivered by generator, P = 75 W

but, we have a relation between : P_average = P_maximum / 2

   thus, P_maximum = 2 (P_average ) = 2 (75) =150 W

   Thus, Torque maximum = τ_maximum = P_maximum / W

   Thus,

maximum countertorque in the generator coil is

   τ_maximum = 150 W / 376.99 = 0.3979 N m

maximum countertorque in the generator coil is 0.4 Nm