Chapter 23, Problem 7CQ

The irregularly shaped area of charge in FIGURE Q23.7 has surface charge density ${\eta }_i$ .Each dimension (x and y) of the area is reduced by a factor of 3.163.

a. What is the ratio Of ${\eta }_f/{\eta }_i$ , where ${\eta }_f$ is the final surface charge density?

b. An electron is very far from the area. What is the ratio $F_f/F_i$ of the electric force on the electron after the area is reduced to the force before the area was reduced?