Cuesta College, San Luis Obispo, CA
Students have a bi-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 what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"That EPE can increase when two like charges (positive-positive, negative-negative) are pushed together or opposite charges (positive-negative, negative-positive) are pulled apart. Also, EPE decreases when two like charges (positive-positive, negative-negative) are left to repel each other or when opposite charges (positive-negative, negative-positive) are left to attract one another."Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"Objects such as batteries can store electrical potential energy or 'voltage.' Changes in EPE are caused by either moving like charges towards each other or opposite charges away from each other since this is doing work. There is still a one-step and a separate two-step approach."
"The direct approach to analyzing electric potential energy is that a source charge q1 stores potential energy EPE on a separate test charge q2. The change in EPE is caused by moving the source charge and the test charge close together or far apart. In the two-step approach, the field model explains that a source charge Q creates an electric field everywhere around itself and thus it exerts a force F on test charge q."
"That there are two different approaches to electric potential energy and both give you the same answer. One involves knowing the source while the other just deals with the effects of that source."
"The formula to calculate electric potential energy is very similar to Coulomb's law except there is no r-squared in the denominator portion of the formula when calculating electric potential energy."
"I learned that source Q creates electric potential V and can be stored with a test q."
"I'm having a hard time understanding this presentation, I feel once I see a few examples in class it will click for me."
"I'm so confused..."
"I am still a bit confused with the differences between electric potential, and electric potential energy. I could use some more practice with different scenarios fro using each."Explain the difference between the units of electric potential V, and electric potential energy, EPE.
"I don't really understand why electric potential energy goes up when two like charges are moved closer together or when two different charges are moved away from one another. Shouldn't it be the opposite since like charges repel one another and opposite charges attract each other which would increase and decrease the distances of the charges from one another respectively. Really just a quick explanation should sort me out right."
"I am struggling with the difference between electric potential and electric potential energy."
"I didn't really understand the 'peak' and 'well' analogies."
"This whole section is pretty confusing. The two-step approach, potential energy. I'm having trouble conceptualizing how it all works rather than just the equations. I need to come to your office hours."
"I've never had a good intuitive understanding of potential energy as it relates to kinetic energy, so I'm having a bit of a difficult time understanding how exactly it applies in different scenarios."
"I understand some of the material. It's just a lot of information and I don't think I have it all down yet."
"Still very confused."
"So far nothing is too confusing."
"I didn't find anything confusing but will know for sure if I have any questions in lecture."
"Electric potential uses joules per coulomb (J/C) while electric potential energy uses joules (J)."
"Electric potential is in units of volts (V). Electric potential energy is in units of joules (J)."
"V is joules per coulombs (J/C) and EPE is newtons times meters (N·m)."
Explain the conceptual difference between the electric potential V, and electric potential energy, EPE.
"V describes the potential to have EPE, whereas EPE is the actual potential to do work?"
"Two charges can contain electric potential energy. Only one charge can be a voltage source."
"A source charge Q can create an electric potential V around itself and is used to store EPE with a separate test charge?"
"EPE is used in the one step model and V is used in the middle of the two-step model."
"I'm not sure how to explain this conceptually."
Briefly summarize the difference (if any) between "voltage" and electric potential.
"I am not certain about the differences between voltage and electric potential. Voltage is the amount of potential at a location. The electric potential is also the amount of potential at a location."
"Potential and voltage really mean the same thing."
"These terms are interchangeable."
"There is no difference between the two. 'Voltage' is just another name for electric potential."
Identify the changes in electric potential energy EPE (if any) for the following test charges (±q):
(Only correct responses shown.)
Positive test charge +q brought closer to a positive source charge +Q: increase [71%]
Negative test charge –q brought closer to a positive source charge +Q: decrease [68%]
Positive test charge +q brought closer to a negative source charge –Q: decrease [55%]
Negative test charge –q brought closer to a negative source charge –Q: increase [55%]
Identify the changes in electric potential V (if any) for the following test charges (±q):
(Only correct responses shown.)
Positive test charge +q brought closer to a positive source charge +Q: increase [55%]
Negative test charge –q brought closer to a positive source charge +Q: increase [45%]
Positive test charge +q brought closer to a negative source charge –Q: decrease [23%]
Negative test charge –q brought closer to a negative source charge –Q: decrease [45%]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I need a review of the difference between EPE and V."
"Please go over some more examples in class."
"So batteries store energy by having a lot of like charges close together?" (That's what capacitors do. Batteries store energy by having dissimilar materials close together, that want to give up or take in electrons from each other via chemical reactions.)
"Do you have the solutions posted anywhere for the previous quizzes?" (Not for all the questions, but there are solutions for some of them; just click on the blog link next to the PDF link for each quiz.)
"Do our pre-lab question responses effect our pre-lab grade?" (As long as you try your best to answer them, you still get full credit. But do try your best; your responses help you figure out how little (or how much) background you need for the briefing at the start of each lab.)
"So the wave strips in lab work because they're sinusoidal waves that are in phase. If they were cosine waves, would they be out-of-phase from the sine waves?" (If both wave strips were cosines, then they would still be in phase sources. If one wave strip was a sine and the other strip was a cosine, then they would be out-of-phase sources, and then to find the maxima angles you would need to use d·sinθ = (m + (1/2))·λ instead of d·sinθ = m·λ.)
"Hey, P-dog how long have you been teaching physics?" (After getting my doctorate, about forty semesters so far, I have to teach sixty more semesters until I get to retire.)
"Hey I was looking at your webpage and do you teach swing classes?" (I don't teach swing dance, but Mrs. P-dog and I sometimes DJ for swing dancing at the Madonna Inn on Mondays.)
No comments:
Post a Comment