Determining the direction of magnetic force

[miyayeah]

Homework Statement

Referring to (b) in the picture above: What is the direction of the magnetic force on the electron?

Homework Equations

I use the right-hand rule where by putting your index finger in the direction of the magnetic field and thumb in the direction of the velocity, the middle finger points in the direction of the magnetic force.

The Attempt at a Solution

I tried the right-hand rule as I explained, but as soon as I put my thumb in the direction of velocity my fingers are restricted and my index finger cannot align with the magnetic field. How should I solve this problem? Any help would be appreciated.

 

[Orodruin]

First of all, only the component of the magnetic field that is orthogonal to the velocity matters, but in this case they are orthogonal, so you should not have a problem in aligning the directions.

Second:

I use the right-hand rule where by putting your index finger in the direction of the magnetic field and thumb in the direction of the velocity, the middle finger points in the direction of the magnetic force.

This is not correct. Your thumb should be pointed in the direction of the current, not the direction of the velocity. I will let you think a bit about in what cases those are the same and in what cases they are not.