Electric Potential Difference diagram

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SUMMARY

The discussion centers on calculating the electric potential difference between two points, A and B, due to two point charges: q = +1.0 nC and Q = -2.0 nC. The correct approach involves computing the potential at each point from both charges using the formula V = ke(q/r). The calculated potentials at points A and B must account for contributions from both charges to determine the potential difference, Va - Vb, which ultimately resolves to 3.6V. Misunderstandings arose from focusing on individual charge contributions rather than the combined effect at each point.

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  • Understanding of electric potential and point charges
  • Familiarity with the formula V = ke(q/r)
  • Knowledge of basic electrostatics concepts
  • Ability to perform calculations involving nanocoulombs and distances in meters
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  • Learn how to calculate electric potential difference in electrostatics
  • Study the principle of superposition in electric fields
  • Explore examples of electric potential calculations with varying charge configurations
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Students studying electrostatics, physics educators, and anyone seeking to understand electric potential calculations in the context of point charges.

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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

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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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