1. The problem statement, all variables and given/known data What is the velocity of a beam of electrons that go undeflected when passing through crossed electric and magnetic fields of magnitude 6.8 kV/m and 4.9 mT, respectively? What would be the radius of the electron's orbit if the electric field were turned off? 2. Relevant equations v = E/B 3. The attempt at a solution I got the first part by using the equation above. (I converted the measurements because I'm looking for m/s). So 6.8 kV/m is 6800 V/m and 4.9 mT is .0049T. v = E/B v = (6800V/m)/(.0049T) v = 1.3877*10^6 m/s For the second part, I am a bit confused as to how to find the radius (which equation to use?).