Question

4. Electrostatics Coulomb’s law, or Coulomb’s inverse-square law, is a law of physics that describes force interactions between static electrically charged particles. The law is: F=kq1q2r2whereq1andq2represent two charges separated by a distance r and k is a constant approximately equal to 9×109Nm2C−2.

(a) Find the work required to bring together a 0.8nCnegative charge and a 0.6nCnegative charge from a distance of 200 mm (0.2 m) to a distance of 100 mm (0.1 m).Note:1nC= 10−9CwhereCstands for coulombs and nC stands for nanocoulombs.

(b) In part (a), is the work done positive or negative? Explain why. How would your answer changeifq1= 0.8nCofpositivecharge and all other data remained the same as above?

(c) Four point charges with charges +Q,−Q,+Q and−Q are respectively arranged on the four corners of a square with unit side length. Find the potential energy of this system.

Answer 1