## 20150316

### Online reading assignment: circuit basics

Physics 205B, spring semester 2015
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 circuit basics.

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.
"The current (symbol I) is defined as the net amount of charge passing per unit time through an area perpendicular to the flow direction. The magnitude of the current tells us the rate of the net flow of charge. A resistor uses up voltage (electric potential energy per charge) as current flows through it."

"How deionized water was not a good conductor. But by adding charges through the ions when salt was added it became a good conductor."

"The most basic circuit that you can build will have an ideal 'electromotive' (emf) source of voltage connected to a resistor, such that charges can flow continuously."

"There are some very dangerous circuits that can be created. High-resistance materials can be used as insulators while low-resistance materials are used as conductors."

"I understand that the direction of a basic circuit is clockwise because the direction is based off the way positive charge would move. Electrons flow counterclockwise. I also understand that current is the same everywhere and doesn't get used up by the bulb."

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.
"I was confused as to why the electrons flow counter clockwise in a circuit. I also did not understand the purpose of the resistor."

"I don't understand why the current flows opposite the flow of electrons. Also, what exactly resistance is or comes from."

"The short circuit results in a low resistance, a very large current. Current is proportional to voltage and inversely proportional to resistance. I just needed to type it out to make sure I'm right?"

"Ohms law is kindof confusing, and how resistance works. I understand that copper wire is a good conductor and wood would be good insulator but how that relates to resistance confuses me."

"The terminology in addition to the numerous equations given in this sections readings were all very confusing. They weren't individually confusing, but rather I'm confused as to how they each relate to each other as a whole."

"I found the differences between battery size and voltages somewhat confusing. I wasn't sure how batteries of the same size could have different voltages."

"I didn't find anything confusing about the assigned reading. I understood all of the concepts and think I grasp them all."

A wire is used to complete a circuit with a single 9.0 V battery. When a wire is used to complete a circuit with a system of 244 "stacked" 9.0 V batteries, there will be __________ voltage and __________ current, compared to the single 9.0 V battery circuit.
 less; less. * [1] less; more. * [1] more; less. ********* [9] more; more. ************************** [26] (Unsure/guessing/lost/help!) *** [3]

An emf source is connected to a container of water. When salt is dissolved in the water, there will be __________ resistance and __________ current, compared to the pure deionized water circuit.
 less; less. [0] less; more. **************************** [28] more; less. ***** [5] more; more. *** [3] (Unsure/guessing/lost/help!) **** [4]

A metal screw completes a "short circuit" with a transformer emf source. This is dangerous due to the very __________ resistance of the metal screw, and the very _________ current flowing through it.
 low; low. * [1] low; high. *************************** [27] high; low. ** [2] high; high. ******* [7] (Unsure/guessing/lost/help!) *** [3]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Resistance is just the amount of non-conducting stuff that electrons must move through in order to complete the circuit, right?" (Basically, yes.)

"My dreams of becoming MacGyver are just within my reach. If only I had a a paper clip, and a stick of gum..."

"Could you keep posting questions from previous quizzes/tests on the homework portion of the blog? I find those super helpful."

"How do you recommend we start studying for the upcoming midterm. After my horrible performance on this last quiz I need to start studying now. Freaked-out and really confused face." ≡(:0)