In Fig. 4.6, p1 and p2 are (perfect) dipoles a distance r apart. What is the torque on p1 due to p2?What is the torque on p2 due to p1? [In each case, I want the torque on the dipole about its own center. If it bothers you that the answers are not equal and opposite, see Prob. 4.29.]

Reference prob 4.29

(a) For the configuration in Prob. 4.5, calculate the force on p2 due to p1, and the force on p1 due to p2. Are the answers consistent with Newton’s third law?

(b) Find the total torque on p2 with respect to the center of p1, and compare it with the torque on p1 about that same point. [Hint: combine your answer to (a) with the result of Prob. 4.5.]

Solution 5P

Step 1 of 5:

Consider two dipoles (p1 and p2) are separated by a distance r. The dipoles produce their own electric dipole fields. Because of the individual electric fields produced by the dipoles, each dipole will tend to rotate. We are going to find the torque on each dipole due to another.