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NEET2015PhysicsCurrent ElectricityActual

A potentiometer wire has length 4 m and resistance 8 Ω . The resistance that must be connected in series with the wire and an accumulator of e.m.f. 2V , so as to get a potential gradient 1 mV per cm on the wire is :

Options

  1. A32 Ω
  2. B40 Ω
  3. C44 Ω
  4. D48 Ω

Correct answer

A. 32 Ω

Step-by-step solution

d V d t   =   1 m V c m For a potentiometer 1   c m of wire has 1   m V of voltage So, 400   c m has 0.4 V . Given R must be connected in series Δ V = 0.4 = 2 8 + R   × 8 8 + R = 16 0.4 = 160 4 = 40 ⇒             R = 32 Ω

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