Help with E&M Questions: Answers, Explanations & Reviews

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The discussion focuses on clarifying concepts related to electromagnetism (E&M) questions. Participants seek help with specific problems, sharing their answers and confusion about formulas like V^2/R and I2R. Key points include the importance of understanding electric potential and its relation to potential energy, as well as the behavior of capacitors in circuits. There are also inquiries about why certain resistances are ignored in calculations. Overall, the thread emphasizes the need for a solid grasp of fundamental E&M principles to tackle these questions effectively.
compscier
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Help with E&M?
1) http://tinyimage.net/images/25790944428468568236.png
I don't even... The answer is B.. What should I review??

2)http://tinyimage.net/images/81684598844478119651.png
Why can't I use the formula V^2/R for this one?? answer C btw ( I did get it right, but just because I didn't see the answer choice I needed had I used V^2/R...)

3)http://tinyimage.net/images/14929814429358178541.png
How do I approach questions like 52? The answer is E... (I get 51 though)

4)http://tinyimage.net/images/89661487184785817963.png
Umm... I don't remember learning this.. What is this an application of?

5)http://tinyimage.net/images/05849919813601766271.png
57:B -> Why is R2 ignored? I put A originally...
58:A -> I thought there is no current after a significant amount of time b/c capacitor takes up all the charge? no?
 
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That's a lot of stuff for one thread !
 
they are sort of simple questions... I guess I'll make separate threads for each then...
 
compscier said:
Help with E&M?
1) http://tinyimage.net/images/25790944428468568236.png
I don't even... The answer is B.. What should I review??
Maxwell's correction to Ampere's Law.
2)http://tinyimage.net/images/81684598844478119651.png
Why can't I use the formula V^2/R for this one?? answer C btw ( I did get it right, but just because I didn't see the answer choice I needed had I used V^2/R...)
Read the question. Its wording basically tells you to use I2R, where R is written in terms of resistivity, length & cross-section.
3)http://tinyimage.net/images/14929814429358178541.png
How do I approach questions like 52? The answer is E... (I get 51 though)
Do you know how to calculate electric potential?
4)http://tinyimage.net/images/89661487184785817963.png
Umm... I don't remember learning this.. What is this an application of?
Review your notes. How is electric potential related to potential energy?
5)http://tinyimage.net/images/05849919813601766271.png
57:B -> Why is R2 ignored? I put A originally...
Initially the potential across the capacitor is zero -- like a short circuit.
58:A -> I thought there is no current after a significant amount of time b/c capacitor takes up all the charge? no?
Eventually, the capacitor will not charge anymore, so there is no current through it, but there is still current through R2.
 
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Thread 'Voltmeter readings for this circuit with switches'

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TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
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Thread 'Correct statement about a reservoir with an outlet pipe'

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The answer to this question is statements (ii) and (iv) are correct. (i) This is FALSE because the speed of water in the tap is greater than speed at the water surface (ii) I don't even understand this statement. What does the "seal" part have to do with water flowing out? Won't the water still flow out through the tap until the tank is empty whether the reservoir is sealed or not? (iii) In my opinion, this statement would be correct. Increasing the gravitational potential energy of the...
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