Question

Magnetism Question: (see photo)

Why is the answer so?

Answer 1

I know that in the right-hand rule (wherein your fingers curl), the thumb points in the direction of the current. How can I find the magnetic force through that?

Answer 2

You're right about the right hand rule for the current. That means at the point where the charge is, the magnetic field is going INTO the screen/page.

Now remember the equation to find the magnetic force on a particle: F = qv x B. This equation is a cross product that tells you that the direction of the force is perpendicular to both the velocity of the particle and the magnetic field itself. Furthermore, we know there will be a net force on the particle because it is not moving parallel to the field.

So now you just need to use the right hand rule a second time to find the direction of the force. Thumb goes in the direction of qv, fingers in direction of B. The direction your palm then faces is the direction of the force. In this case, your thumb points right and your fingers go into the screen/page. Your palm will be facing up, so that's the direction of the force. C is the answer!

Answer 3

Perfect explanation, @matt101 ! Now I know that you can and are supposed to use the right hand rule twice on some occasions. Thank You very much!

Answer 4

No problem!