A resistance of 200hm is connected to a source

Question

A resistance of 20ohm is connected to a source of an alternating  potential v=220sin (100piet). The time taken by the current to change from its peak value to rms value is .     a) 0.2sec  b)0.25sec c) 2.5×10^-33sec

Answer 1

R = 20 Ω
V = 220 sin (100πt)
we know that V = V. sin(ωt)
I = V. sin(ωt) / R
I = 220 sin (100πt) / 20
I = 11 sin (100πt)
Also I_rms = I_peak sin (100πt) and I_rms = I_peak / √ 2
I_peak sin (100πt) = I_peak / √ 2
100πt = π / 4
t = 1 / (4x100)
t = 1 / 400
t = 0.0025 = 2.5 x 10^-3