How can a galvanometer detect electric current?

A galvanometer detects electric current by measuring the deflection of a needle in a magnetic field produced by the current.

A galvanometer is a sensitive instrument that is used to measure small amounts of electric current. It operates on the principle of electromagnetic deflection. When an electric current passes through a coil in a magnetic field, it experiences a torque or rotational force. This force causes the coil, which is attached to a needle, to deflect. The degree of deflection of the needle is proportional to the amount of current passing through the coil.

The galvanometer consists of a coil of wire wound around a soft iron core, which is suspended between the poles of a permanent magnet. The coil is attached to a pointer that moves over a calibrated scale. When a current is passed through the coil, it generates a magnetic field. This magnetic field interacts with the magnetic field of the permanent magnet, causing the coil and attached pointer to rotate. The greater the current, the greater the magnetic field generated by the coil, and the greater the deflection of the pointer.

The scale of the galvanometer is calibrated in such a way that the pointer deflection directly indicates the magnitude of the current. The direction of the current can also be determined by observing the direction of the pointer's deflection. If the pointer deflects to the right, the current is flowing in one direction, and if it deflects to the left, the current is flowing in the opposite direction.

In order to increase the sensitivity of the galvanometer, a high resistance is often placed in series with the coil. This allows the galvanometer to detect very small currents. Additionally, the coil is wound with many turns of wire to increase the magnetic field generated by a given current.

In summary, a galvanometer detects electric current by utilising the principle of electromagnetic deflection. The current passing through the coil generates a magnetic field, which interacts with the field of a permanent magnet to cause a deflection of a pointer. This deflection is proportional to the magnitude of the current and indicates its direction.