JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Current Electricity

The current sensitivity of moving coil galvanometer is increased by

25%

. This increase is achieved only by 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:

(A) $+ 25%$ ✓ Correct
(B) $- 50%$
(C)Zero
(D) $- 25%$

Answer: (A)

Solution

Current sensitivity is

S_{I} = \frac{n B A}{k}

and voltage sensitivity is

S_{V} = \frac{S _{I}}{R} = \frac{n B A}{k R}

. Because the alteration is made so that the coil resistance

R

is unchanged, voltage sensitivity is directly proportional to current sensitivity. A

25%

rise in current sensitivity therefore gives a change of

+ 25%

in voltage sensitivity.

JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Single correct option

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