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

The resistances in the left and right gap of a metre bridge are $40 \Omega$ and $60 \Omega$ respectively. When the bridge is balanced, the distance of the null point from the centre of the wire towards left is