Answer:
40 J
Explanation:
[tex]c_1[/tex] = 4 C
[tex]c_2[/tex] = 2 C
[tex]U_1[/tex] = 20 J
The potential energy is directly proportional to the charge of the particle
[tex]U\propto c[/tex]
[tex]\dfrac{U_2}{U_1}=\dfrac{c_2}{c_1}\\\Rightarrow U_2=\dfrac{U_1c_2}{c_1}\\\Rightarrow U_2=\dfrac{20\times 4}{2}\\\Rightarrow U_2=40\ J[/tex]
The potential energy expected is 40 J