Solving Right Hand Rule Homework with Electric & Magnetic Fields

[jtb93]

Homework Statement

An electron is suspended due to the combination of an electric field and a magnetic field. What is the direction of the magnetic field in this region?

Don't need to solve this, just need to explain the approach to solve it.

Homework Equations

Right hand rule 1- thumb (force), index finger (qV or I), middle finger (magnetic field)
Right hand rule 2- thumb (direction of current), fingers (magnetic field)

The Attempt at a Solution

I assume this is a force problem since there is going to be both magnetic and electric forces acting on the electron. Can I assume that since this is the force problem you'd have to use RHR 1 since it involves force?

 

[Simon Bridge]

Yes it's a force problem ... start with a free-body diagram.
You will need to define "direction" to answer the problem.
The electromagnetic force on the electron is $\vec F = -e(\vec E + \vec v\times \vec B)$ where $\vec v$ is the velocity of the electron.