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A galvanometer has a 50 division scale. Battery has no internal resistance. It is found that there is deflection of 40 divisions when R.B.=2400Ω .Deflection becomes 20 divisions when resistance taken from resistance box is 4900 Ω. Then we can conclude : Note: This question is awarded as the bonus. Now the question is corrected.

Current sensitivity of galvanometer is 20μ A/division

Resistance of galvanometer is 200Ω .

Resistance required on R.B. for a deflection of 10 divisions is 9800Ω .

Full scale deflection current is 2 mA.

Current Electricity

JEE Main level, single correct, medium

365 of 380

Question 365 of 380

A galvanometer has a 50 division scale. Battery has no internal resistance. It is found that there is deflection of 40 divisions when $R.B.=2400\Omega .$ Deflection becomes 20 divisions when resistance taken from resistance box is 4900 Ω. Then we can conclude :

Note: This question is awarded as the bonus. Now the question is corrected.

Show answer and solution

Answer: (A) Current sensitivity of galvanometer is $20\mu A/division$

Current in the circuit,

I=\dfrac{V}{2400+{R}_{G}}and\dfrac{I}{2}=\dfrac{V}{4900+{R}_{G}}

\Rightarrow {R}_{G}=100\Omega

I=\dfrac{2}{2500}=8\times {10}^{-4}A

Current Sensitivity

=\dfrac{{8\times 10}^{-4}}{40}

20\mu A

per division

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