A positive charge moving up enters a magnetic field pointing out of the screen. What is the direction of the magnetic force on the charge?
up
down
right
left
To determine the direction of the magnetic force on a moving charge, you can use the right-hand rule. The right-hand rule states that if you extend your right hand, align your fingers with the direction of the positive charge's velocity, and then bend your fingers in the direction of the magnetic field lines, your thumb will point in the direction of the magnetic force.
In this case, the positive charge is moving up, so you would point your fingers up. The magnetic field is pointing out of the screen, so you would bend your fingers out of the screen. Your thumb will then point to the left. Therefore, the direction of the magnetic force on the positive charge moving up is to the left.