A choke coil and a bulb are connected in series to a $\mathrm{DC}$ source. If an iron core is inserted in the choke coil, is there any change in the brightness of the bulb?

Variation of alternating current $\mathrm{I}$ with time $\mathrm{t}$ is shown in the graph below. Find the root mean square value of the current.  

 An $\mathrm{AC}$ source of $\mathrm{emf} \mathrm{e} = 200 \sin \mathrm{\omega t}$  is connected to a resistor of$50 \mathrm{\Omega }$, Calculate: Average current ($\mathrm{I}$av).

An $\mathrm{AC}$ source of $\mathrm{emf} \mathrm{e} = 200 \sin \mathrm{\omega t}$ is connected to a resistor of $50 \mathrm{\Omega }$. Calculate: Root mean square (rms) value of emf.