PI Problems for the Physics Suite Edward F. Redish |
Problem Name | Comments | Source | Demo (UMd) |
E01. Charged pendula | This problem mixes the issues of understanding electrostatic forces, Newton's third law, and free-body diagrams. As a result, it can be quite challenging. It can be analyzed by students qualitatively without the formal detail so it can be appropriate for a PI problem. It can be matched with a homework problem in which the students have to work out the details. | EFR | J1-21 (repulsion with hanging test tubes) |
E02. Charges in a line | Good for focusing students on the 1/r^{2} dependence of Coulomb's law. | Based on a ranking task in E&M TIPERS by Hieggelke, O'Kuma, Maloney, and Kanim | |
E03. Charges in a Square | A nice next step to E02. Students have to think about vector addition as well as the 1/r^{2} dependence and they have to be careful. Some of the differences are subtle. A simpler starting version is available at E03-a for classes that may have a bit more difficulty with handling vectors. | Based on a ranking task in E&M TIPERS by Hieggelke, O'Kuma, Maloney, and Kanim | |
E04. Motion in an E-Field: 1 | The basic idea of how an E-field translates to forces. Some students may still have trouble recalling Newton's laws and what happens to a particle feeling a constant force. | EFR | |
E05. Force in an E-Field | A comparison of the forces felt by a charge in a uniform E-field. Students tend to see location in the field along the field lines as corresponding to an increased value | Based on a ranking task in E&M TIPERS by Hieggelke, O'Kuma, Maloney, and Kanim | |
E06. Changing the test charge | The E field should be independent of the test charge, but given the equation E=F/q, many students will demonstrate their algebraic skills by changing q in this equation and calculating the field that results, forgetting that F has an (unlabeled) dependence on q. This is a good example for focusing on the need to look at mathematical equations not just as symbols but as ways of expressing physical relationships. | EFR | |
E07. PE in a uniform field | How the PE of a particle released from rest changes -- with reasons. Some students find it tricky to keep track of PE. Making the connection to energy conservation is better after the fact, supporting students having slogged through the relation between force and PE. | EFR | |
E08. Three charges | This problem has students considering how Coulomb's law forces depend on the charge and the distance together. A nice problem for making the students think in symbols rather than numbers. It can help them with learning to map symbols into physical quantities. | EFR | |
E09. Field due to two charged plates | Asks students to describe the electric fields in and around two large and close parallel plates. This is best done in the context of a discussion of superposition and the field from a plate of charge. | EFR | |
E10. Potential due to two charged plates. | Asks students to describe the electric potential in and around two large and close parallel plates. A good follow up to E09. | ||
E11. Which bulb is brighter? | The classic comparison of one bulb, two bulbs in series, and two bulbs in parallel. A ranking task. Left so that possible answers can be draws from the class. | From McDermott & Shaffer, Âm. J. Phys. 60, 994 (1992). |
(one vs. two bulbs in series and parallel) |
E12. Drawing current | Asks which draws more current from a battery, two bulbs in series or two bulbs in parallel. Students often have difficulty seeing current as a response to the pressure of voltage and assume a battery is a constant current source. This problem encourages a discussion of the separation of the idea of voltage and current. | EFR | |
E13. An infinite chain of resistors | Although this looks like a pretty challenging problem to calculate the current for, the qualitative question is straightforward if the students are thinking in terms of a good qualitative model of current flow. Many of the standard analogies are useful here. (Even the actual calculation turns out to be straightforward, but not as useful for building intuition.) | From Mazur, Peer Instruction | |
E14. Short circuit: 1 | A nice qualitative problem using a short circuit. | From Mazur, Peer Instruction |
Maintained by Edward F. Redish
Comments and questions may be directed to
redish@umd.edu
Page last modified April 9, 2007