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Question:

A galvanometer of resistance 100Ω has 50 divisions on its scale and has sensitivity of 20µA/division. It is to be converted to a voltmeter with three ranges, of 0-2V, 0-10V and 0-20V. The appropriate circuit to do so is :

R1=19900ΩR2=9900ΩR3=1900Ω

R1=2000ΩR2=8000ΩR3=10000Ω

R1=1900ΩR2=9900ΩR3=19900Ω

R1=1900ΩR2=8000ΩR3=10000Ω

Solution:

Correct option is D. R1=1900ΩR2=8000ΩR3=10000Ω
20×50×10⁻⁶ = 10⁻³Amp
V1=2
10⁻³ = 100+R1
1900=R1
V2=10
10⁻³ = (2000+R2)
R2=8000
V3=20
10⁻³ = 10×10³+R3
10×10³=R3