Determining a charge at higher potential & potential energy

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Discussion Overview

The discussion revolves around understanding the concepts of electric potential and potential energy, particularly in the context of positive and negative charges within an electric field. Participants explore the relationship between potential and potential energy, as well as how these concepts apply to different types of charges in a given electric field configuration.

Discussion Character

  • Conceptual clarification
  • Homework-related
  • Technical explanation

Main Points Raised

  • One participant expresses confusion about the difference between potential and potential energy, particularly in relation to a positive charge in an electric field.
  • Another participant clarifies that potential energy is calculated as the product of charge and potential (U = qV), suggesting that this relationship is key to understanding the concepts.
  • A participant requests further explanation on how the behavior of potential and potential energy differs for positive versus negative charges.
  • There is a discussion about the implications of having a negative charge in the electric field, with one participant noting that the potential at point B is higher than at point A, but the potential energy behaves differently.
  • Clarifications are made regarding the terminology of "higher" versus "bigger" when discussing potential and potential energy, emphasizing the importance of context in understanding these terms.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the conceptual differences between potential and potential energy, particularly in the context of negative charges. The discussion remains unresolved with multiple viewpoints presented.

Contextual Notes

Participants express uncertainty about the definitions and relationships between potential and potential energy, particularly when considering different types of charges. There are indications of missing assumptions regarding the application of these concepts in specific scenarios.

Who May Find This Useful

This discussion may be useful for students preparing for exams in physics, particularly those grappling with the concepts of electric potential and potential energy in relation to different types of charges.

chococho
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**sorry, the title should probably read determining a point at higher potential and potential energy
So I feel like this is a really simple example, but I have a test tomorrow and this potential and potential energy stuff is really starting to not make sense...

I know that a charge going in the direction of the electric field goes from a higher potential to lower potential and from lower to higher if it's going in the opposite direction.
The problem is that I don't know how potential energy is different from potential.

So a diagram I have has two points A and B and an electric field going from right to left. There is also a positive charge just sitting between A and B. And it says PE for B is bigger than PE for A. Is this just because B is at a higher potential?

I also have a diagram that is the same, but only with a negative charge between A and B instead of a positive charge. This one I'm not really sure about.. I assumed it would be the opposite for a negative charge, but it says Vb is bigger than Va, but Ua is bigger than Ub.

Can somebody help me with this please? The more I think about it the more confusing it gets...
 
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If the potential is V, then the potential energy is qV.

That is, it needs to be multiplied by the charge. You can remember this easily if you are familiar with electron volts: eV. One eV is the energy acquired by an electron moving through a potential difference of 1 volt.
 
Hm, that's something we never learned in class..
Could you also explain the difference between what happens when you have a positive charge or a negative charge in the field?
 
chococho said:
I also have a diagram that is the same, but only with a negative charge between A and B instead of a positive charge.

Now you know that U = qV. If q is negative, what happens to U?

This one I'm not really sure about.. I assumed it would be the opposite for a negative charge, but it says Vb is bigger than Va, but Ua is bigger than Ub.

When you have a quantity that can be either positive or negative, it's less confusing to say "higher" instead of "bigger", and "lower" instead of "smaller". If Vb = (say) 5 volts, and Va = 3 volts, then Vb is higher than Va (Vb > Va).

However, if If Ub = -5 joules, and Ua = -3 joules, then Ub is lower than Ua (Ub < Ua).
 

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