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JEE Main 2018 (16 Apr, Shift 1) · Kirchhoff's Laws & Measuring Instruments

Kirchhoff's Laws & Measuring Instruments question from JEE Main 2018 (16 Apr, Shift 1)

Q171JEE Main 2018 · 16 APR · SHIFT 1Easy

Kirchhoff's Laws & Measuring Instruments

A galvanometer with its coil resistance 25 Ω\Omega requires a current of 1 mA for its full deflection. In order to construct an ammeter to read upto a current of 2 A, the approximate value of the shunt resistance should be:

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Answer: (b)

  1. S=IgGI−IgS = \frac{I_g G}{I - I_g}
  2. S=10−3×252−0.001≈0.0252=1.25×10−2 ΩS = \frac{10^{-3} \times 25}{2 - 0.001} \approx \frac{0.025}{2} = 1.25 \times 10^{-2}\ \Omega
  3. So the answer is (b) 1.25×10−2 Ω1.25 \times 10^{-2}\ \Omega.
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