A proton and an electron are moving in the +x direction in a magnetic field in the +z
direction. What are the directions of the forces on the proton and electron?

Explanation:

Force on a moving charge is given by the following relation

F = q ( v x B )

for proton

q = e  ,   v = vi  , B = Bk

F = e ( vi x Bk )

= Bev - j

= - Bevj

The direction of force is along negative of y axis or -y - axis.

for electron

q = - e  ,   v = vi  , B = Bk

F = - e ( vi x Bk )

= - Bev - j

=  Bevj

The direction of force is along positive  of y axis or + y - axis.

e

explanation:

there is no change in the electric potential energy as it is in rest on both conditions.

double the distance = divide strength by 4