Question

Reading obtained when a voltage of $e=200\sin \omega t+40\sin (3\omega t+30{}^{\circ })+30\cos (5\omega t+21.5{}^{\circ })$ is applied is to an electrodynamometer voltmeter is ________ V.

• A. 140
• B. 145.77
• C. 154.77
• D. 150

Answer 1

The correct option is B 145.77

Electrodynamometer voltmeter reads rms value

$\therefore e_{rms}=\sqrt{{\left(\frac{200}{\sqrt{2}}\right)}^2+{\left(\frac{40}{\sqrt{2}}\right)}^2+{\left(\frac{30}{\sqrt{2}}\right)}^2}=145.77V$