Current Electricity Questions

A potentiometer is an accurate and versatile device to make electrical measurements of $E.M.F.$, because the method involves:

Figure shows a circuit contains three identical resistors with resistance $R=9.0\Omega$ each, two identical inductors with inductance $L=2.0\text{mH}$ each, and an ideal battery with emf $ϵ=18\text{V}$. The current '$i$ ' through the battery just after the switch closed is:

A long solenoid of diameter $0.1\text{m}$ has $2\times 10^4$ turns per meter. At the centre of the solenoid, a coil of $100$ turns and radius $0.01\text{m}$ is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to $0\text{A}$ from $4\text{A}$ in $0.05\text{s}$. If the resistance of the coil is $10{\pi }^2\Omega$, the total charge flowing through the coil during this time is:

The resistance of a wire is ‘$R$ ’ ohm. If it is melted and stretched to ‘$n$ ’ times its original length, its new resistance will be: