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Moving Charges and Magnetism — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsMoving Charges and Magnetism2 Marks
Question
Define current sensitivity and voltage sensitivity of a galvanometer.
Increasing the current sensitivity may not necessarily increase the voltage sensitivity of a galvanometer. Justify.
✓

Answer

The current sensitivity of the galvanometer equals the deflection per unit current.

Alternate Answer

Voltage sensitivity is the deflection per unit voltage.

Alternate Answer

$\frac{\phi}{\text{V}} = \bigg(\frac{\text{NBA}}{\text{k}}\bigg) \frac{\text{I}}{\text{V}} = \bigg(\frac{\text{NAB}}{\text{k}}\bigg)\frac{1}{\text{R}}$

Justification: Increasing the current sensitivity may not necessarily increase the voltage sensitivity. If N→2N, i.e., we double the number of turns, then

$\frac{\phi}{\text{I}}\rightarrow2\frac{\phi}{\text{I}}$

Thus, the current sensitivity doubles. However, the resistance of the galvanometer is also likely to double, since it is proportional to the length of the wire. N→2N, and R→2R, thus the voltage sensitivity, remains unchanged.

$\frac{\phi}{\text{V}}\rightarrow\frac{\phi}{\text{V}}.$

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