20130310

Online reading assignment: electric potential energy

Physics 205B, spring semester 2013
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on electric potential energy.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"I thought it was interesting to see why volts are called volts and how that ties into potential energy and how it also is used in electrical work and why it is used in that way."

"It's all interesting if they could describe it in the book in a way that i could understand."

"I like how energy is stored in an object when acted upon from a field."

"That any two charges can contain electrical potential energy."

"I liked the explantation of why field lines point towards decreasing electric potential values. I didn't quite get why before, but now writing out the math makes it all make sense."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Just understanding how point charges are sometimes fixed, it was confusing how to actually calculate the change in electric potential energy."

"Formulas, formulas everywhere."

"more clarification on V potential and how it is different from UE."

"Why is it that potentials do not have a direction in space? I found the distinction between electric potential and potential energy kind of confusing."

"Just from the reading, the equations do not make sense. I see the values, but do not necessarily know their relations with the problem."

"I'm having a difficult time understanding why the change in electric potential energy is opposite in sign to that of work done."

"I'm not sure why I am struggling with this, but I just can't wrap my head around why placing a positive test charge in a field will have field lines that point in the direction of decreasing potential and potential energy and then placing a negative charge in a field will have field lines pointing in the direction of increasing potential and decreasing potential energy."
Explain the conceptual difference between electric potential V, and electric potential energy, UE.
"UE finds the electric potential energy of two charges (q1 and q2) at a fixed distance from each other. V is the voltage of a test charge, q, at a fixed distance r away from a source charge Q."

"Electric potential V is defined as the electric potential energy per unit charge. UE is the electric potential energy as a function of the position of the moveable charge.

"Electric potential energy UE is the energy that is collected when two similarly charged items come closer together or when oppositely charged items move apart. Electric potential V is the transferring unit of electric potential energy."

"Voltage is a measure of difference. Joules is a measure of energy. In the ubiquitous water metaphor, voltage is like pressure, Joules is like water flow."

"I need more clarification on this. I don't understand the difference."
Briefly summarize the difference (if any) between "voltage" and electric potential.
"Formal and informal."

"Voltage seems to store the potential energy with the test q, but I don't fully understand this concept."

"Electric potential is often shortened to potential. It is also informally called voltage especially in connection with electric circuits."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can you explain the difference between the electric potential and electric potential energy?" (I am certainly going to try. No guarantees.)

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