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Moving Charges And Magnetism

Question
CBSEENPH12037630

Increasing the current sensitivity may not necessarily increase the voltage sensitivity of galvanometer. Justify.

Solution
Let the deflection produced in applying voltage V is φ then,

voltage sensitivity = φv=NBAkR

The voltage sensitivity may be increased by
(i) increasing N, B, A  and, 
(ii) decreasing k.

Current sensitivity is deflection per unit current whic is , given by φI
current sensitivity = NBAk 

It can be increased by 
(i) increasing NBA
(ii) decreasing k. 

There is a factor of resistance R in voltage sensitivity. 

Hence, increasing the current sensitivity may not necessarily increase the voltage sensitivity of a galvanometer.