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betterfuture

2+ Year Member
Feb 16, 2016
594
96
I am kind of having a little difficult time in understanding Electric Potential. I understand that (+) and (-) charges attract and thus want to decrease their potential energy as shown with a (-) sign in their PE. But what I don't understand is how this relates to Electric Potential.

If two positive charges are close together, and if one moves 1 of those positive charges away from the other, you are decreasing their potential energy because positives oppose each other so they are happy with that. However, what can I say about their electric potential?
 

NextStepTutor_2

Vendor
5+ Year Member
2+ Year Member
Apr 29, 2014
278
109
Status
Pre-Medical
I am kind of having a little difficult time in understanding Electric Potential. I understand that (+) and (-) charges attract and thus want to decrease their potential energy as shown with a (-) sign in their PE. But what I don't understand is how this relates to Electric Potential.

If two positive charges are close together, and if one moves 1 of those positive charges away from the other, you are decreasing their potential energy because positives oppose each other so they are happy with that. However, what can I say about their electric potential?
Remember that electrical potential energy is like any other potential energy as you stated above. As such it is measured in Joules. Electric potential, however, is a ratio of energy to charge and is measured in volts (J/C). If EPE is falling, then voltage (aka potential) should be falling as well. Think of potential as the ration of energy to charge.

This is useful when dealing with electrostatics and circuits because rarely do we just move a single charge around (current is charge/time). This if I need to have a certain voltage (i.e. J/C) say 12 volts, then the more charges I try to give that ratio of energy the more total EPE I need.

For example moving a 1C charge from a 0V position to a 10V position (say, on a capacitor), then I would need 10 Joules [1C x (10-0) J/C]. If I needed to do the same thing with 2 C, I would need 2C x 10 J/C = 20 Joules of EPE to move them.

With electrical circuits the total energy is not necessarily as useful as knowing the ration of energy to charge so that when you design circuits, you can use the current to determine how much energy will be delivered to a given component.

THIS LINK should also be a good explanation with pictures.

Hope this helps! Good luck.
 

betterfuture

2+ Year Member
Feb 16, 2016
594
96
So basically, it's just another way of relating the charge's PE to each other. Like, if I expend a certain amount of energy to move a single charge away from some charge, would it increase it's PE from the other stationary charge or decrease it? Is that what it is?
 
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aldol16

2+ Year Member
Nov 1, 2015
5,102
3,756
Status
Medical Student
Remember that electric potential is something that is intrinsic to a charge. It has nothing to do with any other charge. Formally, it's defined as the amount of work required to move a unit positive test charge from infinity to the point at which the potential is measured.
 

betterfuture

2+ Year Member
Feb 16, 2016
594
96
So Electric Potential is moving any charge from ∞ to a point on space, while, I am guessing, Potential Difference measures the Work done between two points in space? Maybe I was mixing the two up.
 

aldol16

2+ Year Member
Nov 1, 2015
5,102
3,756
Status
Medical Student
So Electric Potential is moving any charge from ∞ to a point on space, while, I am guessing, Potential Difference measures the Work done between two points in space? Maybe I was mixing the two up.
Yes, voltage measures the work done to move a unit charge between two points.
 

betterfuture

2+ Year Member
Feb 16, 2016
594
96
So to another point, I was wondering why the Electric Potential of a point moved from ∞ to a point in space is 0. Is it because there was no work done to move the charge against some kind of outside force or field?
 

aldol16

2+ Year Member
Nov 1, 2015
5,102
3,756
Status
Medical Student
So to another point, I was wondering why the Electric Potential of a point moved from ∞ to a point in space is 0. Is it because there was no work done to move the charge against some kind of outside force or field?
I think you're confusing multiple concepts here. Electric potential is an intrinsic property of a point charge and is equal to the work done by moving that point charge in to where it is from infinity.
 
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