During a particular thunderstorm, the electric potential between a cloud and the ground is Vcloud - Vground = 2.9 x 108 V, with the cloud being at the higher potential. What is the change in an electron's potential energy when the electron moves from the ground to the cloud?

Answer 1

The potential energy per electron must decrease by e*(delta V)
= (1.6*10^-19)*2.9*10^8
= 4.6*10^-11 Joules

delta V is positive but e is negative; hence a decrease in P.E.
Clearly a lightning strike could not take place if the change in PE were positive.

Answer 2

-2..4e-11