Question

A moving proton experiences force from a magnetic field. true or false If the charged particle experiences a downward force (towards the bottom of the screen), what is the sign of the charge? true or false If there were an electric field pointing into the computer screen instead of a magnetic field, what would be the direction of force on the charge?

Answer 1

1. Yes a moving proton moving in magnetic field experience a force as long as the direction of motion is not parallel to the direction of magnetic field. In such case the direction of force is given by Cross product of velocity and magnetic field direction.

2. If vxB (i.e cross product of Velocity and magnetic field) points in the downward direction and charge experience force in downward direction then the charge must be negative. On the other hand if the charge experience force in upward direction then it must be negative charge.

3. If electric field is pointing into the screen and charge is positive then it will experience force in the same direction i.e. into the screen. On the other hand if the charge is negative then it will experience force in opposite direction that is towards out of the screen.