Current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is

40 Ω

25 Ω

500 Ω

250 Ω

Solution

250 Ω

Current sensitivity of moving coil galvanometer

$I_{s} = \frac{N B A}{C} . . . . (i)$

Voltage sensitivity of moving coil galvanometer,

$V_{s} = \frac{N B A}{C R_{G}} . . . . . . (i i)$

Dividing equation (i) and (ii)
Resistance of galvanometer

$R_{G} = \frac{I_{s}}{V_{s}} = \frac{5 x 1}{20 x 10^{- 3}} = \frac{5000}{20} = 250 Ω$

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