The deflecting torque in an electrostatic instrument can be calibrated by _______.

Deflecting Torque in Electrostatic Instruments:

Electrostatic instruments measure voltage or charge by utilizing the electrostatic force between charged plates. The deflecting torque in such instruments is proportional to the square of the voltage applied across the plates. This torque causes the pointer to move, and the degree of deflection can be calibrated to measure the voltage accurately.

The deflecting torque (T) in an electrostatic instrument is given by:

T ∝ V²

Where V is the potential difference between the plates. By adjusting the potential difference between the plates, the deflecting torque can be calibrated.

Explanation of Options:

1. Adjusting the potential difference between the plates: - This is correct. By varying the potential difference between the plates, the deflecting torque can be calibrated. This allows the instrument to measure different voltages accurately.

2. Adjusting the damping: - Adjusting the damping affects the speed and stability of the pointer movement but does not directly calibrate the deflecting torque.

3. Adjusting the spring constant: - Adjusting the spring constant affects the restoring torque but does not directly calibrate the deflecting torque caused by the electrostatic force.

4. Adjusting the frequency: - Adjusting the frequency of the applied voltage affects the dynamic response of the instrument but does not directly calibrate the deflecting torque.

Conclusion:

The deflecting torque in an electrostatic instrument can be calibrated by:

1) adjusting the potential difference between the plates