Solve Basic Electricity and Magnetism Questions - No Calculations Needed

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Homework Help Overview

The discussion revolves around basic concepts in electricity and magnetism, including Coulomb's law, energy stored in capacitors, and the behavior of charged particles in magnetic fields. Participants seek clarification on fundamental principles and specific problems without delving into calculations.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants express uncertainty about which equations to apply for specific problems, such as energy stored in capacitors and the implications of the right hand rule in magnetic fields. Some question the assumptions behind their reasoning, particularly regarding the behavior of charged particles in magnetic fields and the nature of electric potential.

Discussion Status

Several participants have offered insights into the use of specific laws and equations, while others are exploring different interpretations of the problems presented. There is an ongoing exchange of ideas, with some participants questioning the validity of their approaches and seeking further clarification.

Contextual Notes

Some participants indicate that the questions are basic and express frustration over the perceived simplicity of the problems. There is also mention of constraints related to homework rules and the expectation of showing work, which influences the nature of the discussion.

compscier
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Yes, yes I know about the template, but these questions are so basic that I don't really know what I can show as work... Sometimes all I need for help is the relevant equation itself -.- So please don't delete or hate. Thanks!


2. http://tinyimage.net/images/50136173150204648365.png
The answer is A and A explain please?


4. http://tinyimage.net/images/85261815545593376175.png
umm the answer is A, and I have no idea what to use...

5. http://tinyimage.net/images/61071039590674115839.png
WHAT WHY IS ISN'T IT 2uJ? THIS DEFIES PHYSICS WAHHH joking lol

6. http://tinyimage.net/images/49749004950847017201.png
I'm guessing you use kirchhoffs law for this...

7. http://tinyimage.net/images/00194558680517153372.png
so i get why 66 is B, but why is 67 B as well?? shouldn't the graph just be the formula shown in 66?

Any help would be appreciated
 
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compscier said:
2. http://tinyimage.net/images/50136173150204648365.png
The answer is A and A explain please?

This really should not be answered, it is so basic. Just use coulomb's law

compscier said:
3. How do you know which formula to use for the energy stored in the capacitor (you know there's 1/2QV and 1/2V^2C...) like for number 61 in http://tinyimage.net/images/82840419860896498375.png

It depends upon the ease of use. In 61 the capacitors are in series so q will be constant. Hence best would be 1/2Q2/C ---> You missed out on this formula
 
Last edited by a moderator:


compscier said:
1. a charged particle is projected parallel to a uniform to a magnetic field, the resulting path is a straight line parallel to the field... why? doesn't the right hand rule apply here

What does the right hand rule say?
 


ashishsinghal said:
This really should not be answered, it is so basic. Just use coulomb's law



It depends upon the ease of use. In 61 the capacitors are in series so q will be constant. Hence best would be 1/2Q2/C ---> You missed out on this formula

1. hmm is electric potential a scalar?

2. So wait, what's wrong here:
1/2*V^2*C=1/2*6*6*(1/(1/6+1/6+1/6))=1/2*36*2=18?
 


Abdul Quadeer said:
What does the right hand rule say?


ahh is it because the angles between velocity of the particle and magnetic field is 0, thus eliminating the force?
 


compscier said:
ahh is it because the angles between velocity of the particle and magnetic field is 0, thus eliminating the force?

Yes your are right.
It is convenient to use right hand rule to find out the direction of force acting on the particle when the magnetic field vector and velocity vector are perpendicular. You may answer this question by using the equation F=q(vxB)
 


compscier said:
1. hmm is electric potential a scalar?

2. So wait, what's wrong here:
1/2*V^2*C=1/2*6*6*(1/(1/6+1/6+1/6))=1/2*36*2=18?

This will give you net energy. BTW 1/2*36*2=36
 


hmm help me on the other ones please?
 


Can't answer 5th.
For the 6th: just do it - nike
For the 7th: you need to tell why are you not getting B for 67
 
  • #10


compscier said:
5. http://tinyimage.net/images/61071039590674115839.png
WHAT WHY IS ISN'T IT 2uJ? THIS DEFIES PHYSICS WAHHH joking lol

2uJ is the work done by the Electric field. The magnetic field does no work.
 
Last edited by a moderator:
  • #11


Abdul Quadeer said:
2uJ is the work done by the Electric field. The magnetic field does no work.

Yeah, that is the point. Since force is perpendicular to the velocity F.ds =0.
 

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