A2L Item 174

Goal: Reasoning about electric fields

Source: 283 ring, E on axis

A ring
of radius R with charge +Q (uniformly distributed) is positioned as
shown. What is the electric field at a point on the axis, a distance x
from the origin?

  1. None of the above.



(4) Discuss how the form of the field can be reasoned from symmetry and units. Together with limiting value as x goes to zero, this uniquely singles out one answer.

A good follow-up activity is to have students sketch a graph of the field and potential along the x-axis.