Find the time required for a `50 Hz` alternating current to change its value from zero to the rms value.

Explanation

Given `f=50 Hz`, `i=i_0 sin omegat`
Peak value `i=i_2/sqrt2`
`i_0/sqrt2 = i_0 sin omega t`
implies ` 1/sqrt2 = sin omega t = -sin(pi/4)`
implies ` pi/4 = omega t`
or `t=(pi)/(4 omega)=(pi)/(4 xx 2pif)`
`=(1)/(8f)=1/(8xx50)`
`=(1)/(400) = 0.0025 s`
`=2.5 ms`