SHUNT

 A galvanometer is used in electrical circuits to detect current and in experiments to determine the null point.

If somehow heavy current happens to flow into the coil of galvanometer, then due to very large deflection the pointer of the galvanometer may strike the 'stop pin' and be broken, or the coil of galvanometer may burn due to excessive heat produced. To save the galvanometer from these possible damages, a thick wire or a strip of copper is connected in parallel with its coil. It is called shunt. Its resistance is very small compared to the resistance of the coil. Therefore, most of the part of the current goes through the shunt and only a very small part goes through the coil. Hence there are no chances of the burning of the coil or the breaking of the pointer.

Shunted-galvanometer is very useful for determining the null-points in meter-bridge and potentiometer experiments. First, the approximate position of the null-point is determined by using the shunted galvanometer. At this stage the current in the circuit is very feeble. Now the shunt is removed from the galvanometer so that full current goes through the galvanometer and accurate position of the null-point is determined.