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Concepts Of Physics MCQ Edition [Volume 2]PhysicsElectromagnetic Induction

As shown in the figure, the wire PQ possesses negligible resistance and is made to slide on the three rails at a constant speed of 5 cm s ⁻¹ . Determine the current in the 10 resistor when the switch S is thrown to the middle rail.

Options

  1. A0.2 mA
  2. B0.1 mA
  3. C0.05 mA
  4. D1.0 mA

Correct answer

B. 0.1 mA

Step-by-step solution

When the switch S is connected to the middle rail, the closed circuit consists of the top rail, the middle rail, the 10 resistor, and the upper segment of the sliding wire PQ . The effective length l of the wire PQ in this circuit is the distance between the top and middle rails: l = 2 cm = 0.02 m The motional emf E induced in this segment is given by: E = Blv Substituting the given values ( B = 1.0 T , v = 5 cm s ⁻¹ = 0.05 m s ⁻¹ ): E = 1.0 0.02 0.05 = 10⁻³ V The current I in the 10 resistor is: I = E R = 10⁻³ 10

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