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# Peer Review

## Physlet Problems: Electrostatics

by Wolfgang Christian

## Ratings

### Overall Rating:

Content Quality:
Effectiveness:
Ease of Use:
 Reviewed: Apr 21, 2001 by Physics Overview: These are examples of using Physlets to present questions regarding electrostatics. Qualitative and quantitative questions are included. The electric field can be displayed by a number of means, including force vectors on charges, vector field plots, and electric field lines. Values for the field can also be displayed.The problems can be used as-is or rewritten to suit the needs of individual instructors. This material is examples of using the Efield Physlet athttp://webphysics.davidson.edu/applets/EField4/Intro.html Learning Goals: To help students gain a better qualitative and quantitative understanding of electric charge, forces, and fields. Target Student Population: Lower Level and Intermediate Undergraduate Prerequisite Knowledge or Skills: Basic understanding of electric charge and fields. Type of Material: Curricular Material (Lecture/Demo or Homework Assignment) using Java applets Technical Requirements: These are examples of the use of Physlets, scriptable building blocks for online physics demonstrations and other learning activities.

### Content Quality

Rating:
 Strengths: These examples show several different ways to view the electrostatic field. Because students often have trouble visualizing fields, these different approaches will be helpful for student learning. Showing the electric field through either color-coded vector field plots or with field lines is powerful.Because they can interact with the simulations by moving charges, students can test their conceptualunderstanding of the material.The examples that compare the field lines with the motion of charges will help change the common misconception that charges move along field lines. The applets are scriptable so that instructors can customize the problems or create others by using these as templates. Concerns: In one example (9.1.2), a "test charge" is shown (as the correct answer to a question) that has no field. This is potentially confusing to students.In example 9.1.3, the units of the electric field should be stated as being given in mks units.General Comments on Quality: These examples fill an important need, to aid students in understanding the concepts of fields. They are perhaps even more useful as examples and/or templates for instructor-customized physlet problems. Most are of excellent quality. A few minor quality issues (aside from those given above) are stated below by problem number:9.1.4 -- The question is vague, and the answer is partial. Not only is the total charge zero, but q1+q4=0 and q2+q3=0. 9.1.ap 2 -- The strings lengthen slightly when the charges are clicked on.

### Potential Effectiveness as a Teaching Tool

Rating:
 Strengths: Recommended Use(s) for Material: Homework; Lecture/Demo; Quiz or Self-study problemsA good mix of qualitative and quantitative problems testing students' understanding of electric charges, forces, and fields. For the most part, the items require active intellectual participation by the students. They are visually informative and flexible, addressing a wide range of examples or concepts in basic electrostatics. Concerns: Use(s) Material is not Suited For: TutorialSome problems are pedagogically weak (see comments below). Effective use of these examples to stimulate student thinking requires minor editing of the HTML pages to remove the answers to the questions.These are basic building blocks for creating effective learning material. As is true for Physlets in general, the effectiveness of the material depends somewhat on how the instructor incorporates it into the class.General Comments on Effectiveness: The following comments on effectiveness are listed by problem number:9.1.1 -- Nice qualitative problem.9.1.2 -- Students will likely zero in on the non-changing field, but will this lead to real understanding on their part?9.1.3 -- The origin of the coordinate system should be shown or explicitly and prominently stated; otherwise students may get the idea that the location of only the test charge is important.9.1.5 -- Good problem, but students probably need a hint.9.1.6 -- Good qualitative problem.9.1.7 -- Nice applet, but not effectively used by the problem.9.1.8 -- Seems like a lot of work for little payoff. Most introductory students would probably need hints.9.1.ap 1 -- A "you know it or you don't problem". Will be frustrating to students who don't.9.1.ap 2 -- The most difficult of the problems. The most obvious way of solving it (looking for static equilibrium) is not easy to set up.9.1.ap 3 -- This requires substantial understanding of fields; most introductory students are not likely to get this (other than by guessing).

### Ease of Use for Both Students and Faculty

Rating:
 Strengths: Instructors with some understanding of HTML coding can take these examples and easily incorporate them into pages for their specific class. Instructors willing to learn the scripting of these applets can change them in a great number of different ways.Students can use these applets in a wide range of different ways, at a very intuitive level. These include dragging charges, double clicking to view field lines, and clicking to measure position and field. Concerns: Students will need some guidance in their initial interactions with these sorts of problems. This includes both learning how to interact with the applet and (more importantly) how to retrieve the desired physical information from the applet.Some HTML editing work will need to be done by instructors to modify these (e.g., remove the answers, put randomness in the problems) if they are to be useful for graded homework.General Comments on Usability: Most of the applets are easy to use and manipulate. For learning how to use Physlets skillfully, Physlets: Teaching Physics with Interactive Curricular Material by W. Christian and M. Belloni is recommended.
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