current is flowing in a ring of radius R in the anticlockwise direction. an electron is moving towards the centre of the ring in downward direction inside the plane with velocity V. its velocity will ? a)increase b)remain same c)decrease d)become zero.

Question

current is flowing in a ring of radius R in the anticlockwise  direction. an electron is moving towards the centre of the ring in downward direction inside the plane with velocity V. its velocity will ? a)increase b)remain same c)decrease d)become zero.

anonymous · Answer

ans is b but how?

anonymous · Answer

If the velocity were to change, a force should be applied on the electron. What force could that be? (Something to do with a current-induced magnetic field perhaps?) And what can you say about the direction of that force?

atlas · Answer

The electric field produced by the current in the ring will be perpendicular to the electric field produced by the moving electron. (Check it out using Thumb's Rule). The two electric fields will have no interaction among themselves and so the velocity remains the same.