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JEE Main20198 Apr 2019Evening ShiftPhysicsElectrostaticsActual

A positive point charge is released from rest at a distance r 0 from a positive line charge with uniform charge density. The speed ( v ) of the point charge, as a function of instantaneous distance r from line charge, is proportional to

Options

  1. Av ∝ r r 0
  2. Bv ∝ ln ⁡ r r 0
  3. Cv ∝ ln ⁡ r r 0
  4. Dv ∝ e + r r 0

Correct answer

B. v ∝ ln ⁡ r r 0

Step-by-step solution

1 2 mv 2 = q ∆ V 1 2 mv 2 = q × λ 2 πε 0 ln ⁡ r r 0 v 2 = qλ mπε 0 ln ⁡ r r 0 v = qλ mπε 0 ln ⁡ r r 0 v ∝ ln ⁡ r r 0

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