Electric Potential Difference diagram

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Homework Help Overview

The discussion revolves around calculating the electric potential difference between two points in the presence of two point charges, specifically a positive charge and a negative charge. The values of the charges and their distances from the points of interest are provided, along with an attached diagram for reference.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the method for calculating electric potential at two points due to multiple charges, questioning the correct approach to find the potential at each point from both charges.

Discussion Status

Participants are actively engaging in clarifying the steps needed to compute the electric potential at points A and B, considering contributions from both charges. Some have expressed confusion about the requirements of the problem, while others have provided guidance on the conceptual framework needed to approach the calculations.

Contextual Notes

There is an emphasis on understanding that both charges influence the potential at each point, and the discussion reflects a need to clarify the distances involved in the calculations. Participants are navigating the complexities of the problem without reaching a definitive consensus on the method yet.

sugz
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Homework Statement


Point charges q and Q are positioned as shown. If q= +1.0 nC, Q = -2.0 nC, a = 3.0m, and b = 4.0m, what is the electric potential difference, Va - Vb? **The question with the diagram is also attached **

Homework Equations


V = ke (q/r)

The Attempt at a Solution


V = (8.99x10^9)[(1.0x10^-9)/4) = 2.2475 V.

The anser is 3.6V though, so I don't understand what I am doing wrong!
 

Attachments

  • Q18.PNG
    Q18.PNG
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You are computing the electric potential at the -2 nC charge resulting from the other. This is not what is being asked for.

How would you compute the potentials at the points A and B?
 
How would you suggest to go about it? Because I tried it with the -2.0nC as well and i still didn't get the right answer :/
 
What you are trying is not what is being asked for.

How would you compute the potential at the point A resulting from the upper charge?
 
what do you mean by the upper charge?
 
The upper charge in your image is the 1 nC charge.
 
The potential at that point would be V=ke(q/r), where q is the 1 nC charge and r is a?
 
Yes. So what would be the potential at that same point from the other charge?

In the same fashion, what would be the potential at B from both charges?
 
So the potential at A is V= (8.99e9)(1e-9)/3 = 2.9967 V. The potential at B is V= (8.99e9)(-2e-9)/4 = -4.495 V?
 
  • #10
No, you need to compute the potential at both points using both charges and the correct distances.
 
  • #11
I'm sorry but I am quite confused right now and I really don't understand how to go about this question! Do you mind explaining conceptually why i have to find the potential at each point for both charges?
 
  • #12
Because both charges contribute to the potential at both points and you are interested in the potential difference between the points. The situation is not that of a single point charge.
 
  • #13
Oh that's what I was forgetting, thank you! It makes so much more sense now! :)
 

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