The electron moving through an electric field of 500 N/C and a magnetic field of 0.10 T experiences no force. The speed of the electron has to be determined given that the electron's direction of motion is mutually perpendicular to the fields.
A force due to magnetic field on a charge q moving at a velocity v is equal to F = (q*v)xB . This force is perpendicular to the direction in which the electron is moving and to the magnetic field. An electric field E causes a force equal F = q*E to act on the electron. The direction of the force is opposite to that of the electric field as the electron is negatively charged. The resultant force of the two fields on the electron is 0.
This gives (q*v)*0.1*sin 90 = 500*q
=> v = 500/0.1 = 5000 m/s
The electron is moving at a speed equal to 5000 m/s.