Question

A voltmeter connected across a 60Hz ac source reads 240V. Write down the expression of the instantaneous voltage as a function of time.

Answer 1

240 volts is the rms value of the voltage......
thus find the Vmax....
and equation of the instantaneous voltage as a function of time is Vmax sin (wt)
where w=2*pi*60

Answer 2

Also, V(rms) = V(max)/sqrt(2)