Online reading assignment: magnetic forces from fields

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 magnetic forces from fields.

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.
"The physics gang signs that we need to represent...ha ha."

"I found the 'Crouching Tiger, Hidden Dragon' right-hand rule gang signs pretty funny. I will definitely represent."

"This is all new material for me, so it is all interesting to learn about for the first time."

"It is so cool that was can create a magnetic field with electricity!"

"It is nice to see the railgun in class. It is a popular weapon in science fiction, showing up in Halo, MechWarrior, and A Certain Scientific Railgun."

"How you can use hand symbols to help you remember the direction of forces. Very helpful."

"I thought that it was awesome how some bacteria can navigate by using small crystals of magnetite within the cell to point find their direction north. The bacteria will then swim along the magnetic field line until they return to their home in the mud. I have always been fascinated by biology and the complexity of even the smallest organisms."

"That cutting a magnet in half just creates another N- and S-tipped magnet."

"The railgun was super interesting because I use it when playing Quake 3 and it was way fun."

"I like the right-hand rules because something like these are not something you normally do in a class and they will be helpful to remember the direction of the force exerted from the magnetic field."

"I think its interesting that a metal wire creates its own magnetic field around it by carrying a current."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The railgun didnt make much sense..."

"Everything was confusing, I don't really understand the two-step model, and how the B field comes into play."

"I found pretty much all of the magnetic stuff confusing. I'm lost."

"Just having a hard time figuring out exactly how to use the right hand rule."

"I was having trouble understanding the direction of magnetic force and the right hand rule. Since magnetic force is in three dimensions how do we deal with the z-axis?"

"Vectors and how they go together, and cross product."

"The whole magnetic field thing is throwing me on a loop. Need help!"

Although they will be helpful, I will need some practice with these right-hand rules, because they seem a little confusing they are just described and not shown."

"I don't understand the right-hand/left-hand rules."
Explain what velocity a charged particle might have if it does not experience a force from a magnetic field.
"High velocity, too high for the magnetic field to affect it."

"Its velocity would have to remain constant."

"The charge may be at rest with zero velocity."

"If the point charge is at rest or if its motion is along the same line as the magnetic field then the magnetic force is zero."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can you go over calculating magnetic force?"

"More real world explanations always help :)"

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