Physics. Imagine a magnetic field pointing into the....?

Question

....plane of a piece of paper. An electron moves across the paper from left to right. the direction of the magnetic force on the electron will be...?

idk..i think it would be either towards the top of the piece of paper or the bottom?! help =]

Answer 1

The direction of the magnetic force is the cross-product of the velocity vector of the particle and the direction vector of the magnetic field (this is always true in general for the direction of the force - F_B = B x V, where F_B is the force to due the magnetic field, B is the magnetic field, V is the velocity and all three quantities are vectors). The magnetic field points into the paper (consider "into" the paper the negative direction and "out of" the paper the positive direction) and the electron moves left (consider left negative and right positive). Since both quantities are negative, crossing them gives a positive in the direction that is perpendicular to both (up and down the page). So, the force points to the top of the piece of paper. You could also use the right-hand rule to verify this.

Answer 2

North, up.

It is  Not coming out of the paper towards you to be clear. Use the right hand rule.