The current sensitivity of a moving coil galvanometer increases by 35%, when its resistance is increased by a factor 3. The voltage sensitivity of galvanometer changes by a factor
The voltage sensitivity of a galvanometer is given by:
Voltage Sensitivity = Current Sensitivity/R
If current sensitivity increases by 35% and resistance increases by a factor of 3,
voltage sensitivity changes by:
Change = 1.35/3 = 0.45 or 45%
Answer: (B) 45%
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The current sensitivity of a moving coil galvanometer is given by:
Si = N AB/K
Where:
N = Number of turns
A = Area of coil
B = Magnetic field
K= Torsional constant
When the resistance (R) of the galvanometer increases by a factor of 3, the voltage sensitivity (Sv) is given by:
Sv = Si/R
Since current sensitivity increases by 35%, we have:
Sv′ = 1.35 × Si/3R = 1.35/3 × Sv = 0.45 × Sv
Hence, the voltage sensitivity decreases by 55% (100%−45%
Answer: (C) 55%
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