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Question
A moving coil galvanometer has a resistance of 25Ω and gives a full scale deflection for a current of 10mA. How will you convert it into a voltmeter having range 0 - 100 V?
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Solution
Given: G = 25 Ω, Ig = 10 mA = 10 x 10–3 A,
V = 100 V
To find: Resistance (Rs)
Formula: `R_s = V/I_g - G`
Calculation: From formula,
`R_s = 100/(10 xx 10^(-3)) - 25
= 104 – 25
= 10000 – 25
= 9975 Ω
A resistance of 9975 Ω should be connected in series.
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