Question

A current I given by I = – 8 + 6\(\sqrt{2}\) (sin (ωt + 30°)) A is passed through three meters. The respective readings (in ampere) will be?

(a) 8, 6 and 10

(b) 8, 6 and 8

(c) – 8, 10 and 10

(d) -8, 2 and 2

I got this question during an interview.

I'd like to ask this question from Problems Involving Standard Time Functions in portion Application of the Laplace Transform in Circuit Analysis of Network Theory

Answer 1

Correct choice is (c) – 8, 10 and 10

For explanation: PMMC instrument reads only DC value and since it is a centre zero type, so it will give – 8 values.

So, rms = \(\sqrt{8^2 + \left(\frac{6\sqrt{2}}{\sqrt{2}})^2\right)}\) = 10 A

Moving iron also reads rms value, so its reading will also be 10 A.