We have designed and classroom tested many activities that you can use along with this textbook. In order not to give away the things that students are expected to discover during these activities, each activity appears in the book only as a prompt that self-study students or students who must miss a class can use on their own to mimic the experience of the in-class activity. In the subsequent section of the book is a short summary of the things we would hope a student would learn from the activity, but not a solution to the activity.
It may be helpful, when thinking about electrostatic potentials, to model the physical situation with real objects. It will be helpful to have a collection of different types of balls to represent charges, a set of axes to indicate your choices of origin and of coordinate system, and a voltmeter with two probes attached. Then $\rr$ is the vector that points from your origin to the probe of the voltmeter. (Which probe? Where should the other probe be attached?). $\rr'$ is the vector that points from your origin to one of the balls (charges). $\rr-\rr'$ is the vector that points from the ball to the active probe of the voltmeter. $|\rr-\rr'|$ is the distance between the active probe of the voltmeter and the charge.
An activity that goes along with this section of the book is:
Note: The activities are part of a separate website. If you click on the link above, you will need to use the “Back” button to return here.