A resistance of $20$ ohms is connected to a source of an alternating potential $V = 220\,sin\,(100\,\pi t)$. The time taken by the current to change from its peak value to r.m.s value is

Three alternating voltage sources $V_1$ = $3 sin \omega t $ volt , $V_2= 5  sin(\omega t + \phi _1)$ volt and $V_3 = 5  sin(\omega t -\phi_2 )$ volt connected across a resistance $R= \sqrt {\frac{7}{3}} \Omega $ as shown in the figure (where $ \phi_1$  and $ \phi_2$   corresponds to $30^o $ and $127^o $ respectively). Find the peak current (in Amp) through the resistor

If instantaneous current is given by $i = 4\cos \,(\omega \,t + \phi )$ amperes, then the $r.m.s$. value of current is

An $ac$ generator produced an output voltage $E = 170\,sin \,377\,t\,volts$, where $ t $ is in seconds. The frequency of $ac$ voltage is......$ Hz$

What are $DC$ signals and $AC$ signals ? Why do we preferred an $AC$ signal ?

The voltage of domestic ac is $220$ $ volt$. What does this represent