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Question
Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity. Explain, giving reason.
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Solution
The current sensitivity of a moving coil galvanometer is given by `(nBA)/k`, where n is the number of turns , A is the area of the coil , B is the magnetic field strength of the poles and k is the spring's constant of the suspension wire.
Similarly, voltage sensitivity is given by `(nBA)/(kR)`, where R is the resistance of the wire.
From the above two expressions, we get:
Voltage sensitivity = Current sensitivity/R
Thus, on increasing the current sensitivity, voltage sensitivity may or may not increase because of similar changes in the resistance of the coil, which may also increase due to increase in temperature.
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Reason: A circular coil produces a uniform magnetic field around itself when an electric current is passed through it.
