Question

The sensitivity of a moving coil galvanometer can be increased by

• A. decreasing the number of turns
• B. decreasing the area of the coil
• C. increasing the magnetic field
• D. increasing the torsional constant of the spring
• E. using a thicker wire

Hint:

In modern galvanometers, "increasing B" is achieved by using a strong permanent horseshoe magnet and placing a soft iron core inside the coil to concentrate the magnetic flux.

Answer 1

The Correct Option is C

Concept:
Physics - Moving Coil Galvanometer.
Step 1: Recall the formula for current sensitivity.
Current sensitivity ($I_{s}$) is defined as the deflection per unit current: $$ I_{s} = \frac{\theta}{I} = \frac{NAB}{k} $$ Where:

• $N$ = Number of turns in the coil.
• $A$ = Area of the coil.
• $B$ = Magnetic field strength.
• $k$ = Torsional constant (restoring torque per unit twist) of the spring.

Step 2: Evaluate the variables.
To increase $I_{s}$, we can:

• Increase $N$, $A$, or $B$ (Numerator).
• Decrease $k$ (Denominator).

Step 3: Compare with the options.
Option (C) suggests increasing the magnetic field ($B$), which directly increases the sensitivity.