The household supply of electricity is at `220 V` (rms value) and `50 Hz`. Find the peak voltage and the least possible time in which the voltage an change from the rms value to zero.

Explanation

Here `E_(rms) = 220 V`,
Frequency `=50 Hz`
(a) `E_(rms)= (E_0)/sqrt2`
implies `E_0 = E_(rms)sqrt2`
`=sqrt2 xx 220 xx 1.414`
`34.08 V = 311 V`
(b) Time taken for the current to reach the peak value = Time taken to reach the 0 value from r.m.s.
`i=i_0/sqrt2`
`i_0/sqrt2 = i_0 sin omega t`
`omegat = pi/4`
`t=pi/(4 omega) = pi/(4 xx 2 pi f)`
`=pi/(8pi50) = 1/400`
`=2.5 ms`