Electric field strenth question

[dev-hud]

A Crossed-field velocity selector has a magnetic field of magnitude 1.0 x 10^-2T. What electirc field strenght is required if 10.0 keV electrtons are to pass through undeflected?


ef - 1.0 x 10^-2

I know it gives magnetic field, except how and what formula do we use to figure out the electric field strenght when we are also given 10.0 keV?

 

[collinsmark]

A Crossed-field velocity selector has a magnetic field of magnitude 1.0 x 10^-2T. What electirc field strenght is required if 10.0 keV electrtons are to pass through undeflected?

ef - 1.0 x 10^-2

You should write down the relevant equations for the magnetic forces and the electric forces. You'll find that your answer of "ef - 1.0 x 10^-2" isn't quite right. Some of the relevant equations are a function of velocity.

I know it gives magnetic field, except how and what formula do we use to figure out the electric field strenght when we are also given 10.0 keV?

"10.0 keV" is a measure of energy; kinetic energy in this case, to be specific. Do you know of any unknown variables in your magnetic or electric field/force equations that you might be able to determine if you happened to know the kinetic energy of the electrons?