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JEE Main 2021 (25 Jul, Shift 2) · Kirchhoff's Laws & Measuring Instruments

Kirchhoff's Laws & Measuring Instruments question from JEE Main 2021 (25 Jul, Shift 2)

Q124JEE Main 2021 · 25 JUL · SHIFT 2Medium

Kirchhoff's Laws & Measuring Instruments

The given potentiometer has its wire of resistance 10Ω\Omega. When the sliding contact is in the middle of the potentiometer wire, the potential drop across 2Ω\Omega resistor is:

Figure

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Answer: (c)

  1. Each half of the wire is 5 Ω5\ \Omega; the 2 Ω2\ \Omega is in parallel with the half on the A side.
  2. 5∥2=107 Ω5 \parallel 2 = \frac{10}{7}\ \Omega, total R=107+5=457 ΩR = \frac{10}{7} + 5 = \frac{45}{7}\ \Omega
  3. I=20×745=289 AI = \frac{20 \times 7}{45} = \frac{28}{9}\text{ A}
  4. V2Ω=289×107=409 VV_{2\Omega} = \frac{28}{9} \times \frac{10}{7} = \frac{40}{9}\text{ V}
  5. So the answer is (c) 409\frac{40}{9} V.
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