“How to Convert a Galvanometer into an Ammeter?”

Galvanometer – Definition

A galvanometer is a sensitive electromechanical instrument used to detect and measure small electric currents. It operates on the principle that a current-carrying coil placed in a magnetic field experiences a torque.
It is often the backbone of many analog measuring devices.

Galvanometer – Construction

A typical moving-coil galvanometer (the most common type) consists of the following parts:

A Strong Permanent Magnet: Usually a horseshoe (U-shaped) magnet with concave pole pieces to create a radial magnetic field.

A Rectangular Coil: A fine wire coil (made of copper) wound on a lightweight non-metallic frame. This coil acts as the current carrier.

A Soft Iron Core: A cylindrical piece of soft iron placed inside the coil. It concentrates the magnetic field lines and ensures the field is always radial (parallel to the coil’s plane), making the torque proportional to the current at all angles.

Suspension/Taut Strip: The coil is suspended between two springs or metallic ribbons. These act as the current leads and provide the restoring torque.

A Pointer and Scale: A long, lightweight needle attached to the coil moves over a calibrated scale to indicate the deflection.

Bearings/Pivots: Allow the coil to rotate freely with minimal friction.

Moving Coil Galvanometer – Working Principle