Question

The peak value of an alternating emf is given by $E=E_{0}cos\left(wt\right)$ is 10 volt and its frequency is 50 Hz. At a time $t=\left(\frac{1}{600}\right)$ second, the instantaneous value of the emf is:

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

Answer 1

The correct option is C $5\sqrt{3}V$

E = $E_0$ Cos wt
= 10 cos [2 $\pi$nt]
$=10cos[2\times \pi \times 50\times \frac{1}{600}]$
= 10 cos $\left(\frac{\pi }{6}\right)$
$=10\times \frac{\sqrt{3}}{2}=5\sqrt{3}$V