Question

A proton with a velocity in the positive x-direction enters a region where there is a uniform magnetic field b in the positive y-direction. You want to balance the magnetic force with an electric force so that the proton will continue along a straight line. The electric field should be in the

Answer 1

Explanation:

The magnetic force acting on a charged particle is :

$F=q(v\times B)$

Here q = +q (for proton)

v is in +x direction

B is in +y direction.

So,

$F=q(vi\times Bj)\\\\F=qvB\hat{k}$

It is clear that the magnetic force is acting +z direction. So, to balance the magnetic force with an electric force so that the proton will continue along a straight line, the electric force must act in -z direction.