How do I calculate the electric potential

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Homework Help Overview

The discussion revolves around calculating the electric potential "V" of a point charge "q" at a specific radius "r," particularly when the potential is defined as zero at a distance other than infinity. Participants explore the implications of this setup and the associated equations.

Discussion Character

  • Conceptual clarification, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the formula V=K(q/r) and question its application when the potential is defined as zero at a distance of 1 meter instead of infinity. There are inquiries about the implications of setting the zero point of electric potential at different locations and how this affects calculations.

Discussion Status

The conversation is ongoing, with participants expressing confusion about the implications of defining the electric potential as zero at a distance other than infinity. Some have offered insights into potential differences and the concept of arbitrary constants, while others are questioning the validity of the assumptions being made.

Contextual Notes

There is mention of a professor assigning problems where the electric potential is zero at various distances, which seems to challenge the conventional understanding that V=0 at infinity. This raises questions about the setup and interpretation of the problem.

nroquet
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How do I calculate the electric potential "V" of a point charge "q" at radius "r" if I am told that the electrical potential is zero at a distance "d" other than infinity? I believe that there is some arbitrary constant that must be found but I don't know if, where, or how that fits in.

Formulas I know:
V=K(q/r)
V=U/Q (where U is the potential energy)

Thank you very much if you can help!
 
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If V at r = (Kq)/r, and at infinity V = 0. What is the difference ? Ask yourself why at infinity, the V = zero.
 
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The V=0 at infinity because as r goes to infinity, the function becomes infinitely small.

But what if V=0 at 1meter? Then how would I find V at .5 meters? for some reason the equation V=K(q/r) doesn't work by itself in this case. The only way I can reconcile this is if there is some other part to the equation that we leave out because V=0 is usually at infinity. Any ideas?!
 
nroquet said:
The V=0 at infinity because as r goes to infinity, the function becomes infinitely small.

But what if V=0 at 1meter? Then how would I find V at .5 meters? for some reason the equation V=K(q/r) doesn't work by itself in this case. The only way I can reconcile this is if there is some other part to the equation that we leave out because V=0 is usually at infinity. Any ideas?!

Is this a book question or are you having a problem with a concept? Where did you get V = 0 at 1, at r =1 ? Doesn't V = 0 at r =1 a contradiction if the equation is Kq/r? wouldn't V = kq at 1?
 
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Exactly my problem. My professor assigned a few problems where V=0 at different distances (not infinity). Supposedly it doesn't matter where you set the zero of electric potential (just like it really doesn't matter where you choose the zero of gravitational potential), I just can't figure out how the equation should be set up.
 
This is how you find the potential due to a uniformaly charged sphere, or simply a charge :

DV=change in V= potential difference=V2-V1=(Kq)/r2 - (Kq)/r1
= (Kq)[1/r2 - 1/r1]
at r1= infinity , V1= 0 Which is how you get a voltage value at a distance outside a charge, you assume r1 is infinite distance. If you really say your teacher said you can get a zero voltage. My oh my:frown:
 
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