Question

In order to increase the sensitivity of a moving coil galvanometer:
A. The magnetic field should be increased
B. The suspension wire should be made stiff
C. The area of the coil should be reduced
D. The number of turns in the coil should be reduced

Answer 1

Hint: The principle behind the working of a moving coil galvanometer is that a current-carrying coil placed in a magnetic field experiences a torque, the magnitude of which depends on the strength of the current.

Formula used:
${\text{NIBA = k}}\theta $, where, $N$=number of turns in the coil, $I$ is the current flowing through the coil,
$B$=Magnetic field, $A$=area of the coil, $k$=torsion constant, $\theta $=the deflection of the galvanometer

Complete step-by-step solution:

Sensitivity of a galvanometer:
A galvanometer is sensitive if it shows a large scale of deflection even when a small current is passed through the circuit or a small voltage is applied across it.

Current sensitivity:
It is defined as the deflection produced in the moving coil galvanometer when a unit current flows through the circuit.

Voltage sensitivity:
It is defined as the deflection produced in the galvanometer when a unit potential difference is applied across its ends.
Therefore, the deflection torque is counterbalanced by restoring torque using a spring system equating both will give,
${\text{NIBA = k}}\theta $, then we can write the formula of current sensitivity as, $\dfrac{\theta }{{\text{I}}} = \dfrac{{{\text{NBA}}}}{{\text{k}}}$

This means that the magnetic field is directly proportional in the increase of sensitivity.

Hence, Answer:- The correct option is (A).

Note: By increasing the number of turns in the moving coil galvanometer the sensitivity of the coil can be increased.
By increasing the magnetic field within the circuit, the sensitivity of the moving coil galvanometer can be increased.
By increasing the area of the coil used in the moving coil galvanometer the sensitivity can be increased.
By decreasing the torsion constant, the sensitivity of the moving coil galvanometer can be increased.