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JEE Main 2019 (11 Jan, Shift 2) · Kirchhoff's Laws & Measuring Instruments

Kirchhoff's Laws & Measuring Instruments question from JEE Main 2019 (11 Jan, Shift 2)

Q169JEE Main 2019 · 11 JAN · SHIFT 2Medium

Kirchhoff's Laws & Measuring Instruments

A galvanometer having a resistance of 20 Ω\Omega and 30 divisions on both sides has figure of merit 0.005 ampere/division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 volt, is:

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Answer: (c)

  1. Full scale current (30 divisions one side) Ig=30×0.005=0.15 AI_g = 30 \times 0.005 = 0.15\text{ A}
  2. R=VIg−G=150.15−20R = \frac{V}{I_g} - G = \frac{15}{0.15} - 20
  3. R=100−20=80 ΩR = 100 - 20 = 80\ \Omega
  4. So the answer is (c) 80 Ω80\ \Omega.
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