An alternating current I in amperes varies with time t in seconds as I = 4 sin(200 $\pi$ t). The r.m.s. values of the current and frequency are

Correct Answer: (B) 4/$\sqrt{2}$ A and 100 Hz

Comparing I = 4 sin(200 $\pi$ t) with standard equation I = I_0 sin($\omega$ t), the peak current I_0 = 4 A, so r.m.s. current is I_rms = I_0 / $\sqrt{2}$ = 4 / $\sqrt{2}$ A. The angular frequency $\omega$ = 200 $\pi$ = 2 $\pi$ f gives frequency f = 100 Hz.