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 generators.
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.
"A moving charge feels force from a magnetic field, the direction of which can be determined using the RHR1 or the LHR1 depending on the sign of the charge. A stationary charge does not feel the force from a magnetic field."
"How motion can be converted into electrical current. I know that single-pass generators have to be reset, but continuous generators do not."
"Single-pass generators can only be used once before being reset, while continuous can continuously provide electricity without a need for being reset. Motional emf requires a rod in motion to generate emf."
"Single-pass generators are those which can be used once and then have to be reset. In order to reset these systems you have to bring them back in the opposite direction which will create a motional emf and current but with opposite polarity."
"When a rod moves through a magnetic field the electrons within the rod experience a force and the rod becomes positively charged on one end and negatively charged on the other, and that is how it becomes a battery."
"I seem to have a pretty decent understanding of how a generator works."
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.
"Where do I start, I'm really having a hard time trying to figure out how to use the hand symbols such as 'Hidden Dragon, Crouching Tiger.' I don't really understand how do you use the field model."
"How to orient my hand to not snap my wrist."
"RHR2 and RHR3."
"Motional emf and electric energy. I do not understand how to use the right-hand rule to find the direction of force."
"I don't know what 'motional emf' means. And I don't understand the right-hand rules either."
"Pretty confused on how to use the right-hand rule to find the direction of the force from a single-use generator."
"Overall, this whole chapter is really confusing. It's taking me a long time to get the hang of it."
"I was confused by the rail and hoop-drag generators."
"I don't understand the differences or main parts of the examples of single-use generators. It felt like I was reading gibberish."
"I think I would just need some explanation and demonstration of the different generators to get a better grasp on what they actually do and how they work. Other than that, I felt like this wasn't too hard to wrap my head around."
"I am not quite sure how changing the area of a coil can induce an emf."
up ↑. ************* [13] down ↓. ********** [10] left ←. [0] right →. ****** [6] into the page ⊗. ** [2] out of the page ⊙. * [1] (No direction, as this quantity is zero.) * [1] (Unsure/guessing/lost/help!) *** [3]
in towards the center of rotation. ******** [8] out away from the center of rotation ***************** [17] into the page ⊗. * [1] out of the page ⊙. ** [2] (No direction, as this quantity is zero.) [0] (Unsure/guessing/lost/help!) ******** [8]
Explain what a generator is supposed to "generate."
"A potential difference."
"An electrical current."
"A generator coverts mechanical energy (usually rotational) into electricity (emf)."
"Generators generate a motional electromotive force and current."
Explain the meaning of "motional" in the term "motional emf."
"Well, the moving bar is a source of an electromotive force, called motional emf. An emf is generated by the motion of the bar. "
"When a rod is moved through a magnetic field in order to gain a charge. The motion and magnetic field causes the rod to have electrons (and the fictitious positive charges) moved to one side which essentially creates a battery."
"The moving bar is the motional part that generates emf."
"The bar has to stay in motion!"
"I don't understand what this means."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"When using RHR1, does the force (represented by the middle finger) point out the way your finger tip is pointing. Or does the force point in towards your palm?" (For positive charges, the force on it points the way your middle finger tip points, out away from your palm.)"
"I could use more help on the right-hand rules."
"Generators are interesting because they turn mechanical energy into electricity."
"Seeing the man on the bicycle-driven generator took me back to my childhood days when I was watching Pokémon. I remember an episode where a man was generating power by using a stationary bicycle. On another note, I need to do more research to understand this topic."
"I need to study."
"I think I know why you're so ecstatic about the zombie apocalypse. You either know when it's going to happen or you will bring it about, but you won't tell us. You may tread on thin ice if you make light of a serious topic." (I am the Night King. #winteriscoming #whatisdeadmayneverdie)
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