Question

An alternating current (in ampere) varies with time t as $I=3sin\omega t+4cos\omega t$. The rms value of the current is

• A. $\frac{3}{\sqrt{2}}A$
• B. $\frac{4}{\sqrt{2}}A$
• C. $\frac{5}{\sqrt{2}}A$
• D. $\frac{7}{\sqrt{2}}A$

Answer 1

The correct option is C $\frac{5}{\sqrt{2}}A$

In the pharos diagram representation

$I_0=\sqrt{4^2+3^2}=5$
$I_{nms}=\frac{I_0}{\sqrt{2}}=\frac{5}{\sqrt{2}}$