What is Voltage really?

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Hello, i was wondering if somebody could give be a better explanation of what voltage really is. Its has been explained to me that the voltage of an electron can be thought of as holding a ball at certain height representing the potential energy of the ball which is then converted into kinetic energy as the ball falls and that voltage is kind of like that. I was wondering if there is any more clear explanation for what voltage really is, as this analogy does not really explain what allows electrons to have different amounts of energy, as an battery can not just move an electron higher up, Thanks.

Just a thought but could voltage be thought of as the speed of an electron?
 

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  • #2
Simon Bridge
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The description you have is the accurate description of what voltage is.
"Voltage" is a casual term used to refer to the difference in electric potential between two places. It is derived from the SI unit used to measure it.

See: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elevol.html
Voltage is not properly though of as the speed of an electron any more than the gravitational potential can be though of as the speed of a mass. Much as a mass on a shelf has gravitational potential energy (so the shelf has a gravitational potential) and yet is stationary, an electron may have electrical potential energy, and so be in a position that has a voltage, and yet be stationary: ie if it is levitated between plates of a capacitor.
 
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  • #3
sophiecentaur
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a better explanation of what voltage really is
You seem to be after a 'more familiar' explanation, rather than a 'better' one. Potential Difference is very well defined in conventional EE and that is the best thing to stick with. Trying to re-state such definitions in friendlier terms can lead you up the garden path eventually.
That may seem to be an elitist remark but EE is a very well structured study and has answered all the more straightforward questions - where QM and Relativity are not involved. So it is as well to go along with it and follow the existing rules of the game.
 
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I think the analogy still works. Why does a ball held up high have more energy than a ball resting on the ground? Why does that extra energy get converted when it moves towards the ground?

Same as an electron moving between two points with a voltage.
 
  • #5
sophiecentaur
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I think the analogy still works. Why does a ball held up high have more energy than a ball resting on the ground? Why does that extra energy get converted when it moves towards the ground?

Same as an electron moving between two points with a voltage.
That statement adds nothing to the conventional description. It is just in your own words. The only difference is that you use the word "electron" which is more specific than the word "charge", which covers more possibilities. Also, the question "why" is not in the spirit of true Science which does not try to answer it.
 
  • #6
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Energy is only part of the equation. Voltage is the ratio of energy to charge. If you double the amount of electric charge, voltage will be cut in half for a given amount of energy.
 
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Voltage is simply the amount of work (which is force integrated with respect to distance) you need to do on a charge, per unit charge in moving the charge between two points in an electric field.
 
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That statement adds nothing to the conventional description. It is just in your own words. The only difference is that you use the word "electron" which is more specific than the word "charge", which covers more possibilities. Also, the question "why" is not in the spirit of true Science which does not try to answer it.
It was not intended that the statement add to the conventional description. It was intended to explain how the analogy remained applicable. We are in a teaching forum, after all.
 
  • #9
sophiecentaur
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It was not intended that the statement add to the conventional description. It was intended to explain how the analogy remained applicable. We are in a teaching forum, after all.
If you want an answer to the question about "why the energy gets converted", it's because the Potential energy of a falling body is transferred to kinetic. When a charge moves through a conductor, any change in Electrical Potential is because work is done (as in a motor) or the conductor heats up (Resistance). If a car goes downhill with the brakes on, its original Potential Energy is transferred to heat in the brakes plus a bit of KE due to its small but finite speed downhill.
The "analogy" that you are looking for is valid because Potential is a concept which applies to all sorts of fields.
 
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I do not see the point of this conversation. My comment was directed at the original poster to assist with their understanding.
 
  • #11
sophiecentaur
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I do not see the point of this conversation. My comment was directed at the original poster to assist with their understanding.
Well, yes but we all expect to have ideas in our posts to be challenged to some extent. That's what tends to happen on forums.
 
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Voltage is like water pressure,think squirt gun, high voltage but low amps (amps==amount of water), open garden hose, low voltage, high amperage, firehose, high voltage with high amps, very powerful, its important your analogies keep the relationship between volts/amps
While no analogy will capture the true relationship as well as mathematics does, it can be useful in getting a grip on the concepts.
 
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Well, yes but we all expect to have ideas in our posts to be challenged to some extent. That's what tends to happen on forums.
You don't challenge anything, you misunderstood my intentions and then added your own response.
 
  • #14
sophiecentaur
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You don't challenge anything, you misunderstood my intentions and then added your own response.
You could, perhaps, have stated it differently. You used the "why" word twice and that is not very appropriate - for reasons I have already given and that is what I was challenging, mainly. If you would take issue with that then hear what Richard Feynman has to say about the "why" question. (Easy to find on Youtube).
 
  • #15
sophiecentaur
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Voltage is like water pressure,think squirt gun, high voltage but low amps (amps==amount of water), open garden hose, low voltage, high amperage, firehose, high voltage with high amps, very powerful, its important your analogies keep the relationship between volts/amps
While no analogy will capture the true relationship as well as mathematics does, it can be useful in getting a grip on the concepts.
You could have added the idea that Pressure times flow rate gives an indication of Power. That strengthens the analogy.
 
  • #16
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Voltage is simply the amount of work (which is force integrated with respect to distance) you need to do on a charge, per unit charge in moving the charge between two points in an electric field.

What do you mean by "unit charge"? Would it be correct to put the charge upon which the work is being done in the denominator instead?
 
  • #17
sophiecentaur
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What do you mean by "unit charge"? Would it be correct to put the charge upon which the work is being done in the denominator instead?
The Unit Charge would be the Coulomb in the SI system. Using the word "unit" means that the formula can be applied to any system of units.
In gravitational theory, the Unit Mass tends to be used so that SI or Imperial units can be used with the same formulae.
 
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Thank you. What if the amount of charge being energized is not one coulomb? (Or not one unit of whatever system you use to measure charge?)
 
  • #19
Drakkith
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Thank you. What if the amount of charge being energized is not one coulomb? (Or not one unit of whatever system you use to measure charge?)

Then your numbers change, but the concept remains the same.
 
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  • #20
sophiecentaur
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Then your numbers change, but the concept remains the same.
I had the privilege of learning my first few years of Physics with Imperial Units and then grew up to use cgs, MKs and then SI. I had to forget the number 32(ft/s2 then learn 981cm/s2 then finally moved on to 9,81m/s2 for the acceleration due to gravity but the formulae remained the same. Coulombs were always the same unit for my charges though as I didn't use esu's and emu's in anger (at least I don't remember them at A level).
 
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  • #21
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Voltage is simply the amount of work (which is force integrated with respect to distance) you need to do on a charge, per unit charge in moving the charge between two points in an electric field.

The Unit Charge would be the Coulomb in the SI system. Using the word "unit" means that the formula can be applied to any system of units.

In that case we have a physical quantity (work) in the numerator, and a unit of measure in the denominator. Since we're not allowed to mix and match, either of these would be correct:

voltage = energy/charge
volt = joule/coulomb
 
  • #22
sophiecentaur
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voltage = energy/charge
If you're wanting it to be bombproof, I would suggest:
Potential Difference = Energy transferred / Unit charge
Then you can put in the actual amounts of the quantities involved and get a useful answer.
The rule of thumb to carry with you would be:
One Volt is one Joule per Coulomb - which is totally Unit specific and would be no good for discussing with an inhabitant of the Planet Zog although the Engineer next door would understand what you mean.
 
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  • #23
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This is not going to be an answer to the thread but I would like to say that in my opinion voltage is hard to understand because daily and common physical phenomena are not taught to us in terms of energy. Cars have speed when in motion and we measure it in km/h, we don't make any reference to it's kinetic energy. The cup on the table is "x" meters above the floor but you would not expect anyone to tell you it's potential energy. Someone out there is pushing a box and there's a force acting but the work done on the box is not relevant to the one pushing it. When I as a student came acroos my EM course at college I was taught that explaining things in terms of energy specially in electricity would simplify them instead of talking about forces. I think my teacher was right when he said the analysis would be simpler but the concept became indeed much more complicated. I then decided to take my time to understand the concept of voltage, some day I might fully get it, or I might not :)
By the way, you can always repeat to yourself in the mirror "volts are Joules per Coulomb". Never forgot that advice from Sophiecentaur
 
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  • #24
sophiecentaur
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I was taught that explaining things in terms of energy specially in electricity would simplify them instead of talking about forces. I think my teacher was right
Absolutely. Firstly, Energy is a scalar so you can forget about Directions and, secondly, you can always rely on the totality of the Energy remaining the same. With forces, there is always the consideration as to whether you have equilibrium or not and the possibility of an odd force turning up. Circuit analysis is based on Energy and when people try to introduce forces and fields they really should take into account the actual layout of all the wires etc. - yet they seem to feel that it is somehow easier tograsp what's happening. It's all the fault of the "Volts are a Force" merchants.
 

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