Moving Coil Galvanometer

Topic Content:

A galvanometer is one of the most sensitive and accurate devices for detecting and measuring extremely small currents or potential differences. It is calibrated for use as a milliammeter.

Structure of a Moving Coil Galvanometer:

It consists of a rectangular coil of wire ABCD , wound around a soft iron cylinder or core (armature) placed between the two curved pole pieces of a horseshoe magnet. This arrangement produces a radial or uniform magnetic field in the air gap between the soft iron cylinder and the pole pieces.

The coil is pivoted on jewelled bearings or conducting rods so that it can rotate in the magnetic field when an electric current is passed through it.

The rectangular coil is connected to two phosphor-bronze control springs or hairsprings by two conducting rods.

These springs are made of a conducting material and also act as the “terminals” of the galvanometer, connecting it to an external electric circuit.

Current is led into and out of the coil by the two control springs wound in opposite