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Conductors: Instructor's Guide

Main Ideas

Students explore the properties of conductors.

Students' Task

Estimated Time:

Students work in small groups to solve Griffiths Problem 2.36

Prerequisite Knowledge


Activity: Introduction

Short lecture on the properties of conductors, following Griffiths Section 2.5.

  1. $E=0$ inside a conductor
  2. $\rho=0$ inside a conductor
  3. Any net charge resides on the surface
  4. A conductor is an equipotential
  5. $E$ is perpendicular to the surface just outside a conductor

Activity: Student Conversations

  • Charges are free to move – This is a surprisingly difficult problem for students. Many students do not try to reason about charges moving, which is where all of the properties come from.
  • Charges distributed on the surface – Many think that the charge is distributed on the surface (instead of the charge polarizing the conductor).
  • Overgeneralizing the “balancing” – Some groups overgeneralize the idea of fields “balancing” and thought that the field inside the cavities would be zero.

Activity: Wrap-up

Students also had a difficult time at the end of the activity articulating what they had learned from this problems, so there was an assigned homework problem that asked them to do so.


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