Electric Potential Energy Question

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Homework Help Overview

The discussion revolves around calculating the work done in moving a test charge in the electric field of a charged sphere, as well as determining the number of electrons associated with the charge of the test object. The subject area includes concepts of electric potential energy and charge interactions.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants explore the use of the electric potential energy formula and question how to apply it to find the work done. There is uncertainty about whether to combine distances and how to correctly calculate the potential difference. Some participants clarify their understanding of the equations involved and the steps needed for both parts of the problem.

Discussion Status

Participants are actively discussing the calculations needed for both parts of the question. Some guidance has been offered regarding the use of formulas, but there is still a lack of consensus on the correct approach to find the work done in part a).

Contextual Notes

There is mention of specific distances and charge values, as well as the need to clarify the application of formulas in the context of the problem. The participants are working within the constraints of a homework assignment, which may limit the information they can use or the methods they can apply.

wilson_chem90
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A test charge of +1.0 x 10^-6 C is 40 cm from a charged sphere of 3.2 x 10^-3 C.

a) How much work was required to move it there from a point 1.0 x 10^2 m away from the sphere?
b) How many electrons were gained or lost from the test object.



Relevant equations:
Ee = kq1q2/r
N = q/E

I know how to find b) but for a), I'm not sure if i had to add the two distances together then subtract the charges and divide it by the new distance. anyways, the help would be much appreciated thanks.
 
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Find the potential at 0.4 m and 100 m due to the charged sphere.
Find the potential difference between these two points. Multiply this with test charge to find the work done.
 
just to clarify, i need to use E = kq1q2/r for both distances, and i use the sphere and test charge for both calclations. and then i subtract the answers, and multiply it by the test charge?
 
wilson_chem90 said:
just to clarify, i need to use E = kq1q2/r for both distances, and i use the sphere and test charge for both calculations. and then i subtract the answers, and multiply it by the test charge?
If you use the potential energy formula, i.e. E = kq1q2/r, you need not multiply the answer by the test charge.
 
actually for b), just to make sure. I use N = q/e
the calculation would be:
N = (1.0 x 10^-6 C) / (1.6 x 10^-19 C)
= 6.25 x 10^12 electrons gained or lost
 
the question is b) How many electrons were gained or lost from the test object to create the charge.
 

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