Galvanometer

Intermediate

A coil in a magnetic field deflects with current.

A coil in a magnetic field twists against a spring in proportion to the current, moving a pointer. It is the base of analogue meters.

Worked example

Typically full-scale 50 μA.

Common mistake

Sensitive and delicate.

In more detail

A galvanometer is a sensitive instrument that detects small currents, often using a coil in a magnetic field. It is the basis of analogue meters.

Early analogue meters used galvanometers to display readings.
Galvanometers are used in some bridge and null-detection circuits.
Early ammeters and voltmeters used a galvanometer, where a coil turns and a needle shows the current.

How is a galvanometer converted to an ammeter?

By adding a small parallel shunt resistor.

How is it converted to a voltmeter?

By adding a large series resistor.

What drives the coil in a galvanometer?

The torque from the magnetic field acting on the current in the coil, which turns it against a restoring spring.