Question

A produces a voltage that is given by $V = 240\sin 120t$, where t is in seconds. The frequency and r.m.s. voltage are

• A. 60 Hz and 240 V
• B. 19 Hz and 120 V
• C. 19 Hz and 170 V
• D. 754 Hz and 70 V

Answer 1

Answer: (C)

19 Hz and 170 V

Answer 2

$\nu = \frac{\omega}{2\pi} = \frac{120 \times 7}{2 \times 22} = 19\mspace{6mu} Hz$

$V_{r.m.s.} = \frac{240}{\sqrt{2}} = 120\sqrt{2} \approx 170\mspace{6mu} V$