The eddy current loss in an a-c electric motor is 100 watts at 50 Hz. Its loss at 100 Hz will be

The eddy current loss in an a-c electric motor is 100 watts at 50 Hz. Its loss at 100 Hz will be

(A) 25 watts 
(B) 59 watts
(C) 100 watts 
(D) 400 watts

Explanatory answer:

Eddy current losses is proportional to square of frequency 
( f^2)

In thise case frequency is doubled, so the New loss proportional to (2f)^2

New loss is proportional to 4f^2

Eddy current loss at 100 HZ is = 4 times greater
                                                     =  400 watts