Question

The frequency of an alternating voltage is 50 cycles/sec and its amplitude is 120V. Then the r.m.s. value of voltage is(a) 101.3V(b) 84.8V(c) 70.7V
(d) 56.5V

Answer 1

answer : option (b)

explanation : given, frequency of an alternating current voltage, f = 50 cycles /sec

amplitude of the ac voltage , $V_0$ = 120V

we know, formula $V_{rms}=\frac{V_0}{\sqrt{2}}$

where $V_{rms}$ denotes root mean square value of voltage , $V_0$ peak value of voltage or amplitude .

so, $V_{rms}=\frac{120}{\sqrt{2}}$

= 60√2

= 60 × 1.414 = 84.84 V

hence, option (b) is correct