Tangent galvanometer is an early measuring instrument for small electric currents.
Its working is based on the principle of the tangent law of magnetism, which states that when a current is passed through a circular coil, a magnetic field is produced at the center of the coil in a direction perpendicular to the plane of the coil.
Our instrument comprises of an insulated copper coil wound on a non-magnetic bobbin of Bakelite, about 162.5 mm in diameter.
The copper wire consists of three sets of windings, with 2, 50 and 500 turns, fitted with 4 terminals, for connection to the coils and is marked for each coil.
This frame is mounted on a non-magnetic tripod metal base, supported by leveling screws.
The coil can be rotated on a vertical axis passing through its centre.
A compass box (Magnetometer) is mounted horizontally at the centre of the ring. It is detachable and can be used separately for magnetometer work.
It has an aluminium dial, 100mm in diameter, graduated 0-90° four times, an anti-parallax mirror, and an agate centered magnetic needle fitted with an aluminium pointer designed to provide adequate damping.