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A simple pendulum of mass ' m ', length ' l ' and charge ' + q ' suspended in the electric field produced by two conducting parallel plates as shown. The value of deflection of pendulum in equilibrium position will be

Options

  1. Atan - 1 q mg × C 1   V 2 - V 1 C 1 + C 2 ( d - t )
  2. Btan - 1 q mg × C 2   V 2 - V 1 C 1 + C 2 ( d - t )
  3. Ctan - 1 q mg × C 2   V 1 + V 2 C 1 + C 2 ( d - t )
  4. Dtan - 1 q mg × C 1   V 1 + V 2 C 1 + C 2 ( d - t )

Correct answer

C. tan - 1 q mg × C 2   V 1 + V 2 C 1 + C 2 ( d - t )

Step-by-step solution

Let E be electric field in air Tsinθ = qE Tcosθ = mg tanθ = qE mg Q = C 1 C 2 C 1 + C 2 V 1 + V 2 E = Q A ϵ o = C 1 C 2 C 1 + C 2 V 1 + V 2 A ϵ o C 1 = ϵ 0 A d - t ⇒ E = C 2 V 1 + V 2 C 1 + C 2 ( d - t ) Now θ = tan - 1 q · E mg θ = tan - 1 q mg × C 2 V 1 + V 2 C 1 + C 2 ( d - t )

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