Quick question on sign convention for Work in Columbs

Click For Summary

Homework Help Overview

The discussion revolves around the sign convention for work in the context of electrostatics, specifically involving Coulomb's law and electric fields. Participants are exploring the implications of charge interactions and the associated forces and energies.

Discussion Character

  • Conceptual clarification, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are questioning the sign of work done when moving charges apart, considering the repulsive forces between like charges. Others are discussing the application of Coulomb's law and the relationship between potential energy and the motion of charges. There are inquiries about the direction of electric fields and forces based on the right-hand rule.

Discussion Status

Some participants have offered insights into the nature of the forces acting on the charges and the implications for energy changes. There is an ongoing exploration of different interpretations regarding the signs of forces and fields, with no explicit consensus reached yet.

Contextual Notes

Participants are working within the constraints of specific homework problems and equations, such as those related to Coulomb's law and energy considerations in electrostatics. There is mention of potential confusion regarding the presence of electric fields and their relevance to the forces acting on charges.

Alt+F4
Messages
305
Reaction score
0

Homework Statement



http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam1/fa06

Homework Equations



W =F*D

The Attempt at a Solution



I have it solved, now i thought - would be if i put work into the thing to move it but looking at it since both of them are positive charge they are gona wana repel each other to begin with so why is it not +
 
Last edited by a moderator:
Physics news on Phys.org
http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam1/sp06

Why am i stuck on 14 and 15

The equation that i would use would be F = Kq1Q2 / R^2 correct? and all it is is just plug and chug but i am not getting the answer
 
Last edited by a moderator:
Alt+F4 said:
http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam1/sp06

Why am i stuck on 14 and 15

The equation that i would use would be F = Kq1Q2 / R^2 correct? and all it is is just plug and chug but i am not getting the answer

#14 has a variable force acting the whole time Q1 is approaching Q2. This is not a simple matter of finding one force. Fortunately, the problem has been stated in terms of energy, which is a big hint about how it should be approached. What happens to the potential energy of Q1 as it approaches Q2?

For #15 you need to think about the relationship between voltage across a capacitor and the electrical quantity that causes that voltage. What is the same for the three capacitors?
 
Last edited by a moderator:
All right, can u explain this
http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/fa06

Question 15


I assumed it would be positve, so if i do right hand rule, i have force is up so Electric field would have to point down CorrecT? so why is it negative
 
Last edited by a moderator:
Alt+F4 said:
All right, can u explain this
http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/fa06

Question 15


I assumed it would be positve, so if i do right hand rule, i have force is up so Electric field would have to point down CorrecT? so why is it negative

There is no electric field in the problem. The charge q does produce an electric field, but that field has nothng to do with the forces acting on q. You used the right hand rule correctly and found that the force on a positve charge would be upward at the position shown in the diagram. Clearly the force at that point must be downward, so the charge cannot be positive and must be negative.
 
Last edited by a moderator:

Similar threads

  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 6 ·
Replies
6
Views
4K
Replies
6
Views
3K
  • · Replies 13 ·
Replies
13
Views
6K
Replies
5
Views
2K
  • · Replies 9 ·
Replies
9
Views
12K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 21 ·
Replies
21
Views
3K
  • · Replies 17 ·
Replies
17
Views
2K
  • · Replies 5 ·
Replies
5
Views
4K