Question

The peak value of an alternating emf $E$ given by $E=E_{0} \cos \omega t$ is $10 \,V$ and its frequency is $50 \,Hz$. At a time $t=\frac{1}{600} s$, the instantaneous value of the emf is

• A. $10\, V$
• B. $ 5\sqrt{3}\,V $
• C. $5\,V$
• D. $1\,V$

Answer 1

Answer: (B)

$E=E_{0} \cos \omega t=10 \cos (2 \pi \times f t)$
$=10 \cos \left(2 \pi \times 50 \times \frac{1}{600}\right)$
$=10 \cos \left(\frac{\pi}{6}\right)=10 \times \frac{\sqrt{3}}{2}=5 \sqrt{3}\, V$