Chapter 17. Electric potential related to electric potential energy (17-5)

Review

Our discussion in Section 17-2 shows that if a point charge \(q\) changes position, the potential energy change \(U_{\mathrm{electric}}\) depends on both the magnitude and the sign (positive or negative) of \(q\) (see Figure 17-3). We can simplify things by considering the potential energy per charge—that is, the electric potential energy for a charge at a given position divided by the value of that charge. We call this quantity the electric potential and denote it by the symbol \(V\):

We call the charge \(q_0\) the test charge: Its charge has such a small magnitude that it doesn’t affect the other charges that create the electric field in which \(q_0\) moves. Because we divide out the value of \(q_0\), the value of the potential \(V\) at a given position does not depend on the value of the point charge \(q_0\) that we place there. Instead, \(V\) is determined by the other charges that produce the electric field at the position where we place the test charge.