What is the velocity of a beam of electrons that goes undeflected when passing through perpendicular electric and magnetic fields of magnitude 6800 V/m and 6.9×10−3 T , respectively?

The velocity of a beam of electrons is .

Explanation:

Given that,

Electric field,

Magnetic field,    

When electric and magnetic field both act on the particle, the net force is given by :

If the electron moves undeflected, F = 0

So,

So, the velocity of a beam of electrons is . Hence, this is the required solution.

it is a negative acceleration

it is b. absorbs thermal energy