Current Electricity

JEE Main level, single correct, medium

337 of 380

Question 337 of 380

The current sensitivity of moving coil galvanometer is increased by 2525%. This increase is achieved only changing in the number of turns of coils and area of cross section of the wire while keeping the resistance of galvanometer coil constant. The percentage change in the voltage sensitivity will be:

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Answer: (A) +25+25%

The current sensitivity is given as
Si=NBAC{S}_{i}=\dfrac{NBA}{C}.
The voltage sensitivity is
Sv=(NABCR){S}_{v}=\left(\dfrac{NAB}{CR}\right), where RR is the galvanometer resistance.
Since the resistance is constant,
ΔSi=(ΔSv)\Delta {S}_{i}=\left(\Delta {S}_{v}\right)
Hence, the percentage change in voltage sensitivity is,
(ΔSv)=+25\left(\Delta {S}_{v}\right)=+25%.

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