Question

Two stationary positive point charges, charge 1 of magnitude 3.25 nC and charge 2 of magnitude 2.00 nC , are separated by a distance of 42.0 cm . An electron is released from rest at the point midway between the two charges, and it moves along the line connecting the two charges.

What is the speed vfinal of the electron when it is 10.0 cm from charge 1?

Answer 1

The electron will face a force of attraction towards both the charges but the stronger towards charge 1 as it has a larger magnitude of charge and it field will be thus stronger.

Electric potential due to a charge is given by: assuming that the potential is zero at infinity.

The potential at the point when electron is in the middle is :

The potential at the point when electron is 10 cm from charge 1 is :

Applying the Work-Energy theorem for the electron gives:

The final speed of the electron when it is 10 cm from the charge 1 is 6.5976*10⁶ m/s.