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

Options

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 torsional constant of the coil

Answer

To solve the problem regarding how to increase the current sensitivity of a moving coil galvanometer, we can analyze the factors that influence its sensitivity based on the formula for current sensitivity.

### Step-by-Step Solution:

1. **Understanding Current Sensitivity**:
The current sensitivity (S) of a moving coil galvanometer is given by the formula:
\[ S = \frac{n \cdot A \cdot B \cdot \sin(\theta)}{k} \]
where:
- \( S \) = current sensitivity
- \( n \) = number of turns in the coil
- \( A \) = area of the coil
- \( B \) = magnetic field strength
- \( \theta \) = angle of deflection
- \( k \) = torsional constant of the coil

2. **Increasing Magnetic Field (B)**:
- If we increase the strength of the magnetic field \( B \), while keeping all other factors constant, the sensitivity \( S \) will increase. Thus, one way to increase current sensitivity is to increase the magnetic field strength.

3. **Increasing Area of the Coil (A)**:
- Similarly, if we increase the area \( A \) of the coil, while keeping other factors constant, the sensitivity \( S \) will also increase. Therefore, increasing the area of the deflecting coils is another method to enhance current sensitivity.

4. **Increasing Number of Turns (n)**:
- Increasing the number of turns \( n \) in the coil will also contribute to an increase in sensitivity \( S \). More turns mean more induced electromotive force (emf) for the same current, which results in higher sensitivity.

5. **Considering Torsional Constant (k)**:
- The torsional constant \( k \) is in the denominator of the sensitivity equation. A lower torsional constant means the coil can rotate more easily, which increases sensitivity. Therefore, decreasing the torsional constant will also increase current sensitivity.

### Conclusion:
To increase the current sensitivity of a moving coil galvanometer, you can:
- Increase the magnetic field strength (B).
- Increase the area of the coil (A).
- Increase the number of turns in the coil (n).
- Decrease the torsional constant (k).