Kirchhoff's second law is based on the law of conservation of:

In the circuit shown in the figure,if no current flows through the galvanometer when the key $K$ is closed,the bridge is balanced. The balancing condition for the bridge is

Consider the circuit shown in the figure. The current ${I_3}$ is equal to

In the case of a Wheatstone bridge,the balanced condition is.....

In the following Wheatstone bridge,$P/Q = R/S$. If key $K$ is closed,then the galvanometer will show deflection:

What are the uses of a Wheatstone bridge?