The range of voltmeter of resistance ' $G$ ' $\Omega$ is ' $V$ ' volt. The resistance required to be connected in series with it in order to convert it into a voltmeter of range ' $n V$ ' volt, will be

When cell of E.M.F. ' $E_1$ ' is connected to potentiometer wire, the balancing length is $l_1$. Another cell of E.M.F. ' $E_2$ ' $\left(E_1>E_2\right)$ is connected so that two cells oppose each other, then the balancing length is $l_2$. The ratio $\mathrm{E}_1: \mathrm{E}_2$ is

The current flowing in a coil is 3 A and the power consumed is 108 W . If the a.c. source is of $120 \mathrm{~V}, 50 \mathrm{~Hz}$, the resistance in the circuit is

In the following circuit, the current flowing through zener diode is