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JEE Main201912 Jan 2019Morning ShiftPhysicsCurrent ElectricityActual

An ideal battery of emf 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and resistance 5   Ω . The value of R , to give a potential difference of 5 m V across 10 c m of potentiometer wire, is:

Options

  1. A480 Ω
  2. B495 Ω
  3. C395 Ω
  4. D490 Ω

Correct answer

C. 395 Ω

Step-by-step solution

Potential gradient x = 5 × 10 - 3 10 × 10 - 2 = 4 R + 5 × 5 1 ⇒ 1 20 = 20 R + 5 ⇒ 400 = R + 5 R = 395 Ω

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