Question

The r.m.s. voltage of domestic electricity supply is 220 volt . Electrical appliances should be designed to withstand an instantaneous voltage of(a) 220 V(b) 310 V(c) 330 V(d) 440 V

Answer 1

answer : option (a) 310 volts

explanation : it is given that, rms voltage of domestic electricity supply is 220 volts. e.g., $E_{rms}=220$ volts

we have to find instantaneous voltage. e.g., peak value of voltage, $E_{peak}$

we know, $E_{rms}=\frac{E_{peak}}{\sqrt{2}}$

or, $E_{peak}=\sqrt{2}E_{rms}$

now, $E_{peak}=\sqrt{2}\times220$

= 1.414 × 200 = 311.08 volts

hence , Electrical appliances should be designed to withstand an instantaneous voltage of 310 volts [ approximately]