Question

Point charges create equipotential lines that are circular around the charge (in the plane of the paper). What is the potential energy, in nJ, of a 1 nC charge located 2.82 m from a 2 nC charge ?

Answer 1

The potential energy U of a system formed by two point charges separated a distance r is:

`U=k(q_1q_2)/(r)`

Where k is Coulomb's Constant:

`k=8.98755*10^9N(m^2)/(C^2)`

Repace q1=1nC, q2=2nC and r=2.82m to find the potential energy of the system:

`\begin{gathered} U=k(q_1q_2)/(r) \\ \\ =(8.98755*10^9N(m^2)/(C^2))*((1*10^(-9)C)(2*10^(-9)C))/(2.82m) \\ \\ =6.3741489...*10^(-9)Nm \\ \\ \approx6.37nJ \end{gathered}`

Therefore, the potential energy of the system is approximately 6.37 nanoJoules.