Current Electricity

JEE Main level, single correct, medium

335 of 380

Question 335 of 380

For designing a voltmeter of range 50V50V and an ammeter of range 10mA10mA using a galvanometer which has a coil of resistance 54Ω54Ω showing a full scale deflection for 1mA1mA as in figure.

(A) for voltmeter R≈50kΩR\approx 50kΩ
(B) for ammeter r≈0.2Ωr\approx 0.2Ω
(C) for ammeter r≈6Ωr\approx 6Ω
(D) for voltmeter R≈5kΩR\approx 5kΩ
(E) for voltmeter R≈500ΩR\approx 500Ω
Choose the correct answer from the options given below:

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Answer: (A) (A)\left(A\right) and (C)\left(C\right)

The resistance is given by
R=VIg−GR=\dfrac{V}{{I}_{g}}-G
⇒5010−3−54≈50kΩ\Rightarrow \dfrac{50}{{10}^{-3}}-54\approx 50k\Omega
For ammeter,
S=IgGI−Ig⇒S=10−3×54(10−1)×10−3=6ΩS=\dfrac{{I}_{g}G}{I-{I}_{g}} \Rightarrow S=\dfrac{{10}^{-3}\times 54}{(10-1)\times {10}^{-3}}=6\Omega

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