# Right Hand Rule

## Homework Statement

For this given diagram, determine whether the particle is a proton or an electron. 2. The attempt at a solution
Considering at the point where it enters the material.
Using RHR, Velocity is downwards (First Finger), Field is outwards (Middle Finger), Thumb points left but the force is supposed to be to the right so it's an electron.

3. The Problem encountered
The answer says that it's a proton but how can that be. Am I doing my RHR correctly? Can someone explain how it works. Thanks in advance.

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dx
Homework Helper
Gold Member
Why is force supposed to be towards the right? You correctly found that v x B points left at the point where the particle enters the field. The force is F = q(v x B), so if the particle is positively charged, the force will be towards the left and the particle will be deflected towards the left. That's what happens in the picture, so it must be a proton. If q was negative, it would have been deflected towards the right.

For F=Bil, which fingers represent which part?

Is it first finger current, middle finger field and thumb is force?