Students, pretending they are point charges, move around the room acting out various prompts from the instructor regarding charge densities, including linear \(\lambda\), surface \(\sigma\), and volume \(\rho\) charge densities, both uniform and non-uniform. The instructor demonstrates what it means to measure these quantities. In a remote setting, we have students manipulate 10 coins to model the prompts in this activity and we demonstrate the answers with coins under a doc cam.
1. << Total Current, Square Cross-Section | Integration Sequence |
2. << Magnetic Field Due to a Spinning Ring of Charge | E&M Ring Cycle Sequence |
Each of you is a point charge.
- Make a linear charge density.
- How would you measure the value of the density?
- Answer the same questions for surface and volume charge densities.
Tell the students that they each represent a point charge. Do NOT specify that they are each the same charge unless they ask. Then initiate a conversation with the whole class by asking the prompts listed in "Student Conversations," below. Be flexible about the order of the prompts, responding to the ideas brought up by the students.
Note: It helps if the instructor stands on a chair or table so they are high enough to see all the students.
The instructor can wrap up by making an organized table of the notations used to describe the various types of charge densities (\(\lambda\), \(\sigma\), and \(\rho\)) and their dimensions. If there is time, get the students to help generate the table.