A standard cell of $1.0185 \mathrm{V}$ is used with a slide wire potentiometer. The balance was obtained at $60\mathrm{cm}$. When an unknown $\mathrm{emf}$ was connected, the balance was obtained at $82\mathrm{cm}$. What is the magnitude of unknown $\mathrm{emf}$?

The diagram below shows a dual control switch circuit connected to a bulb. Copy the diagram and complete it so that the bulb is switched ON.

A student uses the resistance of a known resistor ($1 \Omega$ ) to calibrate a voltmeter and an ammeter using the circuits shown below. The student measures the ratio of the voltage to current to be $1\times {10}^3\Omega$ in circuit
(a) and $0.999\Omega$ in circuit (b). From these measurements, the resistance (in $\Omega$ ) of the voltmeter and ammeter are found to be close to

Distinguish between ammeter and voltmeter.

The galvanometer deflection, when key $K_1$ is closed but $K_2$ is open, equals ${\theta }_0$ (see figure). On closing $K_2$ also and adjusting $R_2$ to $5\Omega ,$ the deflection in galvanometer becomes $\frac{{\theta }_0}{5}.$ The resistance of the galvanometer is, then, given by [Neglect the internal resistance of battery]: