Answer:
[tex]\Delta U = \frac{Qq}{4\pi\epsilon_0}(\frac{1}{r_2^2}-\frac{1}{r_1^2})[/tex]
Explanation:
The electrostatic potential energy is given by the following formula
[tex]U = \frac{1}{4\pi\epsilon_0}\frac{q_1q_2}{r^2}[/tex]
Now, we will apply this formula to both cases:
[tex]U_1 = \frac{1}{4\pi\epsilon_0}\frac{Qq}{r_1^2}\\U_2 = \frac{1}{4\pi\epsilon_0}\frac{Qq}{r_2^2}[/tex]
So, the change in the potential energy is
[tex]\Delta U = U_2 - U_1 = \frac{Qq}{4\pi\epsilon_0}(\frac{1}{r_2^2}-\frac{1}{r_1^2})[/tex]