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Question:

A moving coil galvanometer has resistance 50Ω and it indicates full deflection at 4mA current. A voltmeter is made using this galvanometer and a 5kΩ resistance. The maximum voltage that can be measured using this voltmeter, will be close to:

40V

15V

10V

20V

Solution:

Correct option is B. 20V
G=50Ω; S=5000Ω; ig=4×10⁻³; V=ig(G+S)
V=4×10⁻³(50+5000)=20.2 volt