Problem 72-6    Source:  Problem elaborated by the author of the site.

Suppose an electron positioned at point A which is at a distance of 4 cm from a charged particle with + 2.0 nC. Find the work required to move the electron to a point B located 20 cm from the particle.

Solution of the Problem 72-6   

We must be aware of the fact that the electron will move under the effect of an electric field generated by the positively charged particle. As the electron is moving from a point close to the charge to a point further away, that is, in the same direction as the electric field generated by the particle, we must perform positive work, as studied in item 3.. Based on eq. 72-08, we can calculate the potential difference between point B and point A. Reproducing the eq. 72-08 for clarity we have:

Substituting the numerical values, we get:

Carrying out the calculation, we find

By calculating the potential difference between the two points and using eq. 72-07, reproduced below, we have:

Substituting the numerical values, we get:

Carrying out the calculation, we find

To find the value of work in eV we must divide the value found in joule by the value of the electron charge, that is