Question

R.M.S value of the sinusoidal waveform q(t)=2.11cos(87.25t+78π÷478.23).

(a) 1.49 V

(b) 1.56 V

(c) 1.12 V

(d) 1.78 V

I got this question in an online quiz.

I want to ask this question from Induction Motors Speed Control topic in section Speed Control of Direct Current Motors & Induction Motors of Electric Drives

Answer 1

Correct option is (a) 1.49 V

Explanation: R.M.S value of the sinusoidal waveform is Vm÷2^½ and r.m.s value of the trapezoidal waveform is Vm÷3^½. The peak value of the sinusoidal waveform is Vm. The r.m.s value is Vrms = 2.11÷2^½ = 1.49 V.