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JEE Main2014PhysicsMagnetic Effects of CurrentActual

A positive charge ' q ' of mass ' m ' is moving along the +x axis. We wish to apply a uniform magnetic field B for time t so that the charge reverses its direction crossing the y axis at a distance d . Then:

Options

  1. AB = mv qd and t = d v
  2. BB = mv 2 qd and t = d 2 v
  3. CB = 2 mv qd and t = d 2 v
  4. DB= 2 mv qd and t = d v

Correct answer

C. B = 2 mv qd and t = d 2 v

Step-by-step solution

The applied magnetic field provides the required centripetal force to the charge particle, so it can move in circular path of radius d 2 B q v= m^2 d / 2 or, B= 2 mv qd Time interval for which a uniform magnetic field is applied t = d 2 v (particle reverses its direction after time t by covering semi circle). t = d 2 v

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