A2L Item 174
- Description: Identify the correct expression for the electric field a distance from the center of a ring of charge.
- Goal: Reasoning about electric fields
- Source: 283 ring, E on axis
- Keywords: Electric Field, Distributed Charges, Electromagnetism
The question for students:
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?
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None of the above.
Commentary for teachers:
Answer
(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.