Question

Determine the direction of the force that will act on the charge in each of the following situations.
A positive charge moving out of the screen in a magnetic field that points upward.
A positive charge moving downward in an electric field that points out of the screen.
A negative charge moving out of the screen in a magnetic field that points out of the screen.

Answer 1

Answer:

1) Magnetic force to the left.

2) Electric force out of the screen.

3) No force.

Explanation:

For positive charges, electric forces are colinear with the field, and magnetic forces are colinear with the vectorial product $v\times B$ (if the charge is negative, is the opposite), so:

Positive charge moving out of your screen, magnetic field upward: magnetic force to your left.

Positive charge moving down, electric field out of you screen: electric force out of your screen.

Negative charge moving out of your screen, magnetic field out of your screen: there is no magnetic force.