Tangent Galvanometer

What is Tangent Galvanometer?

It is an instrument which can detect/measure very small electric currents. It is also called a moving magnet galvanometer.

Tangent Galvanometer - Tangent Galvanometer


Tangent Galvanometer Principle - Tangent Galvanometer


It consists of a horizontal turntable T, having levelling screws. A wooden frame having a coil is mounted on the turntable in the vertical position. The coils have different turns (say 2, 50, 500 etc). One end of each coil is connected to common terminal O and the other ends of each coil are connected to independent terminals.

A circular compass box is mounted at the centre of the coil. It consists of an aluminium pointer and a magnetic needle fixed at right angles to each other. Both aluminium pointer and magnetic needle are free to move over a circular scale divided into four quadrants of 0° to 90° each. A plane mirror is fixed at the base of the compass box to remove errors due to parallax.


  • Levelling- Levelling screws are adjusted such that the wooden frame is exactly vertical and the turntable is exactly horizontal. The needle is free to move.
  • Setting in Magnetic Meridian- Vertical frame is rotated till plane of frame lies exactly parallel to the axis of the magnetic needle. Now the frame lies in the magnetic meridian.
  • Setting of Pointer- Turn the compass box such that pointer comes on 0-0 line of the scale.

Working and Theory:

Allow the current I to flow through the galvanometer. Due to this, magnetic field B is produced at the centre of the coil which is given by-

B = µ0nI/2r ……….(i)

Where ‘r’ is the radius of the coil.

Tangent Galvanometer working - Tangent Galvanometer
According to tangent law,
B = H tan θ ……….(ii)

From (i) and (ii), we have
⇒ µ0nI/2r = H tan θ

Put µ0n/2r = G = Galvanometer Constant
⇒ GI = H tan θ
⇒ I = (H/G) tan θ

Put H/G = K = Reduction factor, It is measured in ampere.
I = K . tan θ

Moving Coil GalvanometerAtom as a Magnetic Dipole or Bohr Magneton
Potentiometer and its ApplicationPhotoelectric Equation of Einstein
Cells in Series and Parallel DerivationMain Features of Photons
Variation of Resistivity with TemperatureUnits, Dimensions and Vectors– NIOS

Comments (No)

Leave a Reply