Question

The current sensitivity of a moving coil galvanometer can be increased by

• A. Increasing the magnetic field of the permanent magnet
• B. Increasing the area of the deflecting coil
• C. Increasing the number of turns in the coil
• D. Increasing the restoring couple of the coil

Answer 1

Answer: (A), (B), (C)

Increasing the number of turns in the coil

Moving coil galvanometer:

1. A moving coil galvanometer is a device which is used to measure the intensity of electric currents.

2. It is a very sensitive electromagnetic instrument that can measure very low currents even of the order of a few milli or microamperes.

3. These types of galvanometers are mainly divided into two types:

3.1 Suspended coil galvanometer

3.2 Pivoted-coil or Weston galvanometer

Current sensitivity of the moving coil galvanometer:

The current sensitivity of the moving coil galvanometer is given by = $\raisebox{1ex}{$nBA$}\!\left/ \!\raisebox{-1ex}{$k$}\right.$

Here $n$= number of turns

$A$= area of the coil

$B$ = magnetic field strength

$k$ = the torsional constant of the spring (restoring couple per unit twist).

Therefore, we can increase current sensitivity by increasing the number of turns of the coil, increasing the magnetic field of the permanent magnet, and also increasing the area of the deflecting coil as evident from the equation.

As in the case of option D, if we increase the restoring couple of the coil $k$, current sensitivity will decrease. Thus, option D is incorrect.

Hence, the correct options are options A, B, and C.