Reading:

  • Griffiths, Chapter 10

Note: two years ago students requested that I not use the term ‘retarded’ to refer to potentials that are delayed. You will definitely encounter that term elsewhere (and Griffiths uses it extensively). It’s historical and it employs the literal use of the word to mean `delayed’, but we decided to use ‘delayed’ in this class, and I will do that again.

You may work together and get help from other students. Your solutions must be written in your own words, without looking at someone else’s solutions while you write them.

Don’t forget the 9 points that we are looking for in your solutions (see Moodle).

In order to make sure you get your context and meaning/make sense points, next to your answers, please put a “c” with a circle around it for context, and an “m” with a circle around it for meaning.


  1. Griffiths 10.12 Calculate the deferred potential of a current loop with increasing current. You’re only calculating the potential at the center, so \(\mathscr{r}\) can be replaced by the distance from the ring to the center.

  2. Griffiths 10.20 A relatively straightforward application of equation 10.72 - the fields derived from the Leinard-Weichert potentials.


We’re only doing the first two (above). You can do the next two if you really want to.

(3) Griffiths 10.24 Glue charge onto a plastic ring and spin it. As in number 1, you’re only calculating the potential at the center, so \(\mathscr{r}\) can be replaced by the distance from the ring to the center.

(4) Griffiths 10.30 A charged rod with constant velocity. You’re asked to verify that your answer is consistent with Leinard-Weichert potential.