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

In the following circuit, the current $\mathrm{I_2}$ is

A galvanometer of resistance ' $G$ ' is shunted by resistance of 'S' ohm. To keep the main current in the circuit unchanged the resistance to be put in series with Galvanometer is