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/sci/ - Science & Math

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5542953 No.5542953 [Reply] [Original]

What is voltage? I feel like I've never found an explanation of it that I've really understood. I don't care for the hydraulic analogy as I feel it leaves some important things out.

So what is voltage?

Why does it matter? (ie. Why do we express electric things in terms of voltage as opposed to current, what's the significance of the term?)

What's going on say when I overclock a computer component form 0.9V to 1.2V, is there more current? Is there more resistance? More charge? What's going on at an atomic level?

Can voltage be measured at a single point or does it always have to be relative to some other point? If so is there a standard for picking a point to measure the voltage relative to?

>> No.5542969

Voltage is the amount of electrons passing through a current. Your desklamp glows brighter because it translates a bigger amount of electron input.

>> No.5542984

>>5542969
Isn't that amperage?

>> No.5542989

They told me it was the same as electric potential or something like that. This makes me think it is the amount of electrons that pass during a certain period of time.

>> No.5542987

voltage is the equivalent of gravitational potential energy, but for an electric field. that is, it's basically the equivalent of height

>> No.5542994

>>5542953
Voltage is a measure of electric potential. It is how much force an electron feels.

>> No.5542995

>>5542984
Ampere is a unit of current.

>> No.5542992

Don't complain about the hydraulic analogy if you obviously don't understand the abstract concept, dude.

>> No.5542998
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5542998

>>5542994
>tfw no force.

>> No.5542999

>>5542994
How does that translate into real world effects?

ie. What happens if you make an electron feel more force? Does it move faster? How does that effect electronics?

>> No.5543001

>>5542969
No, that's Coulombs. Coulombs per time is amperage.

>>5542994
Basically, this is it OP. Voltage is pressure, Amperage is flow.

>> No.5543005

>>5542998
...why did I laugh...fuck you

>> No.5543003

>>5542999
yes it moves faster given the same resistance

that's what ohms law says

>> No.5543009

>>5542999
If an electron has more potential, it can do more. That's why higher voltages can jump higher spans. Thus, this is why we like the hydraulic analogy for simple stuff. More voltage means bigger spark. A millions volts won't kill you, but 15mA will, through the heart anyway. This is why people survive lightning strikes.Amazing voltage, doesn't hit anything terribly important, and amperage is variable.

>> No.5543012

>>5542999

The electron will accelerate faster, yes. Take for instance an older crt monitor, there would would a large voltage difference between the electron source and screen. The electrons would reach great velocities and energies by the time they hit the screen.

>> No.5543017

>>5542999
Think of resistance for instance as a force against an electron. At a high enough voltage this force is overcome and you will see things that are normally insulating becoming conductive.

>> No.5543019

>>5543012
Okay I think I'm beginning to understand better though if electrons move faster when they have more energy then do higher voltages always result in higher currents.

I'm thinking of it this way, greater voltage means faster electrons which means more electrons moving through a given area per unit time meaning more current. Correct me if I'm wrong.

>> No.5543021

>>5542953
Asking what voltage a specific point has is like asking what direction you are. It has to be in relation to something. In this sense, it's not like water or hydraulics, which has pressure per its depth, for example.

>> No.5543030

>>5543019
As some anon already said

What you state is true and is called ohm's law.

Not all materials obey it though

>> No.5543034

>>5542953
Change in electric potential.

>> No.5543035

>>5543019
Stop thinking of it as speed. Voltage isn't speed. You can have a very thin, very high voltage wire that can perhaps pass only a tiny amperage (flow) like in a defibrillator, or you can have large, high amperage (flow) wires with only a few volts. It works exactly like hydraulics in that sense. You can also vice versa, but you can't pass 2A through a wire that's only physically big enough to pass 1A at a given voltage, nor can you increase the voltage to over what the wire can handle (think about it: what happens if you blow up a balloon too fast, or push too much air in at once?). That's kinda how electric welding works though, heating the metal by running an incredible amount of electricity across a point and melting the wires.

>> No.5543039

>>5543034
What is electric potential?

>> No.5543042

>>5543030
Well, not exactly true, because higher voltages can result (and will for the same amount of wattage - since VA=W) in lower amperage. If you have 500w, you can have it as 10a at 50v or 100a at 5v.

>> No.5543047

>>5543039
Energy. The potential to do work.

>> No.5543045

>>5543035
It is very closely related to speed

>> No.5543053

>>5543047
>>5543039
Voltage is potential.

>> No.5543056

>>5543053
What is voltage then?

>> No.5543058

>>5543019
Yes and no. The are generally related by ohms law of I = V/R where I is current V voltage R resistance. However, as someone else mentioned it is not a speed but force, or acceleration of a mass.

>> No.5543065 [DELETED] 

Think of a pipe.

Voltage is the force of the water in the pipe. Current is the amount of water flowing per second. Resistance is the inverse of the diameter of the pipe.

>> No.5543068

>>5543035
>You can have a very thin, very high voltage wire that can perhaps pass only a tiny amperage (flow)

For this to be true the wire would have to have a very high resistance right? According to Ohm's law?

>or you can have large, high amperage (flow) wires with only a few volts

And for this to be true it'd have to be the opposite, low resistance right?

>> No.5543072

>>5543068
right

you may also want to think about power

which is v^2/r or i^2*r

>> No.5543073

>>5543039

It's the work to move a point charge between two oppositely charged plates.
<div class="math">\Delta P.E. = \overrightarrow{W} = \overrightarrow{F}d</div>
<div class="math"> V = \frac{\Delta P.E.}{q} </div>

k = Coulomb's constant
q = Point charge [Coulombs]

>> No.5543075

>>5543068

That's correct. It's why shorting out a battery is such a bad thing. For a very short time you get current diverging off to infinity.

>> No.5543078

>>5543075
ha ha no

>> No.5543082

>>5543078

Ohms law I = V/R, very low R results in very large I. 0 resistance would imply infinite current.

>> No.5543084

>>5543075
An alkaline battery has an internal resistance of about quater of an ohm, so a 1.5 V battery will give maybe 6 amps when shorted

a bit less than infinity

>> No.5543088

>>5543084

6 amps relative to the normal draw of a battery might as well be infinity.

>> No.5543089

>>5543082
only superconductors have zero R.

the batteries own R is significant

you will just get a few amps

>> No.5543090

<span class="math">E = -\frac{dV}{dx}[/spoiler]

>> No.5543103

>>5543084
That's still a divergent function you're using, it is indeed blowing up to infinity for lower R.

>> No.5543114

>>5543103
what the fuck are you on about? if we apply ohms law, infinite current happens with zero resistance.

why do you think zero resistance ever happens with a battery and a conductor?

>> No.5543118

>>5543103
it is "infinite" for zero ohms. otherwise it is finite.

>> No.5543121

>>5543103
How low?

>> No.5543190

>>5542953
Let me try and explain.
Imagine you have two magic containers. One container has a bunch of electrons and the other doesn't. Since electrons don't like being cramped up, they want to spread out to the other container. If you add more electrons, they have a bigger desire to spread out. If the electrons are sitting there, that's a measure of voltage. Now we add a pipe (load) that allows electrons to move to the other container. If we count the number of electrons per second traveling through the pipe, that's a measure of current. Bigger pipes (more load) can move more electrons in less time. Power is the amount of work done and is calculated P=VI. If you have voltage and no current, or if you have current with no voltage, you have no work (power) being done.

>> No.5543231

>>5543114
I was making an interesting example of how you can wind up with extremely large currents. A battery and conductor never have zero resistance and there are no situation of that in real life but they are relatively negligible. Everyone can relate to shorting out a voltage source with spectacular results, thus it is an easy way to recall Ohm's law, especially for someone just learning about electricity.

>> No.5543261

>>5543231
Next time use a car battery + wrench.

>> No.5543272

Voltage: Joules per Coulumb (charge)
Also written as: Electric field (Force per charge) * Meters* Charge
Basically it's the work that will be done by a field on a certain amount of charge. Do not try to understand Ohm's law. Do not try to understand Ohm's law. Do not try to understand Ohm's law. It is violated in pretty much everything else you learn (short circuits, transformers, etc.).
Voltage is not absolute, and must always be measured relative to *something*. However, a common convention is to measure it relative to infinity, and at infinity a positive field will do 0 joules of work on a charge, therefore voltage with respect to infinite distance is a common metric.

>> No.5543279

>>5542953
Voltage is the measure of the tension within the invisible spring between all electric potentials.

Sometimes it pushes(+ +, - -), sometimes it pulls(- +, + -).