"volt"

HallsofIvy

Really?:
From “google answers”: Volt: The unit of electrical potential. One volt is the electrical potential that
will cause one ampere of current to flow through one ohm of resistance.
From “Webster’s Dictionary”: Noun 1. volt - a unit of potential equal to the potential difference
between two points on a conductor carrying a current of 1 ampere when the power dissipated
between the two points is 1 watt; equivalent to the potential difference across a resistance of 1 ohm
when 1 ampere of current flows through it
volt - a unit of potential equal to the potential difference between two points on a conductor carrying
a current of 1 ampere when the power dissipated between the two points is 1 watt;

I recall a text book stating that a "volt" is commonly refered to as a "unit of electromagnetic force" but immediately pointing out that the term "Force" is misleading- that the "force" is more correctly a potential energy.

rayjohn01

Thank you Halls of, for a good accurate and explanatory source DL
try www.plus2physics.com/electrostatics
That is a statement not argument .

chroot

Halls:

Uh... "potential" and "potential energy" mean quite different things.

- Warren

JohnDubYa

Warren is correct. Some of you are providing definitions that confuse the two terms.

As for the definition Halls provided:

Not a bad definition if the term "difference" was inserted after "potential."

A bad definition, since the language assumes that charge must flow in order for the potential difference to be defined. No, the charge in question (not the charge creating the potential difference) does not even have to exist in order for the potential difference to be defined.

Same problem. No charge has to flow in order for the volt to be defined.

Same problem.

Just because it is in print doesn't make it true. (The same applies to my statements, of course, but I think most physicists would agree with me.)

Some of you are simply repeating what you heard. First, make sure that what you heard was correct.

JohnDubYa

By the way, any definition of volt that relies on the definition of the Coulomb is impractical unless current is taught before the potential. Therefore, I like my definition more.

rayjohn01

To John using the accepted resistive definition , a resistor causes power loss into heat
it does so at the rate P = (I^2).R = (energy/sec)
But V = I.R = I. (energy/sec)/I^2 = (energy/sec)/I = energy/Q joules/coulomb
Try Yahoo at the site suggested.
Potential ( electrical) cannot be defined without charge !

JohnDubYa

Am I on Candid Camera?!?!

rayjohn01

To use a mechanical analogue Gravitational potential is given by
workdone( energy ) per unit mass.
In both cases the word potential has been abreviated ( leaving out it's origin ) which the work done by a TEST object ( mass in above) approaching the one in question.
Having defined the energy required for that point the test mass is mentally removed leaving an isolated body with apparent potential -- but the units are defined.
I totally concur that a current is not required but the concept of the test mass IS.

JohnDubYa

Your gravitational potential definition is no better than your electric potential definition.

So let me get this straight. Suppose we have the Earth. Now we place a test mass (say) 100 meters above the surface of the Earth and drop it. Are you seriously suggesting that the amount of potential at a height 100 meters above the surface of the Earth depends on the amount of work done by the test mass on the Earth? Criminy, that has to be an incredibly smalll number since the Earth barely moves at all if the test mass is dropped. It's not even measurable.

Are you a physicist?

rayjohn01

John it's sunday I do not wish to argue - the test mass is taken from the point of interest to infinity read any standard text on the definition of the missleading term 'gravitational potential'. Ray Have a good day.

JohnDubYa

It doesn't matter. The work done on the Earth by the test mass is completely unrelated to the value of the potential due to the Earth. You are simply wrong.

And if you are still unsure why, consider this. Suppose some entity was holding the Earth in place, not allowing it to move at all. Then the work done on the Earth by the test mass would be 0, no matter where you stopped the test mass. So in this situation the Earth would have zero gravitational potential at all points in space. But that is insane, because masses are still gravitationally attracted to the Earth.

It is clear that you are not a physicist. Am I correct?

Metallicbeing

I have a simple water analogy that I use to help new apprentices.

Say you have a water-hose that's filling up a bucket.

- Voltage can be characterized as the pressure moving the water.

- Amperes (Amps) can be characterized by the volume of water passing a given point within a given time.

- Watts can be characterized by the total amout of water used (the bucket).

["You gotta walk before you can run", wisdom from my parents]

chroot

Metallic,

Your analogy with power is simply wrong... power is the rate of expenditure of energy, not the amount of water (charge) that has already flowed through a pipe (wire).

- Warren

rayjohn01

To John ,you are telling me that no work is done on a mass which falls from your hand to the earth ( kinetic) and that no work is done by lifting it from the ground upward (potential) -- thats nonsense and you know it. all you have to do is think of the energy required to launch a space rocket and imagine it does not stop till very far away. ( what in heck did they need fuel for ??
THAT is the definition of 'gravitational potential" it's the work done /rocket. in rocket units from the start point.
I took university physics for 4 years with electrical and electronic engineering and I'm afraid your intuitive idea of what potential stands for is in error. Not only that but you cannot define how to measure it.
The text book definition is a hypothetical mesurement on a test mass it is identical in form to the electrical case.
If we cannot agree lets call it quits since it not getting either of us anywhere. Regards Ray.

Metallicbeing

Watts are "Static"

Watt/hrs. are "Rate"

I meant that "the bucket" symbolizes total power used in an instance of time.

chroot

Absolutely incorrect.

1 watt = 1 joule per second, where the joule is a unit of energy.

The "watt per hour" is, shall we say, a unit you don't come across often unless the power in some circuit is changing.

You may be confusing your terms with the watt-hour (NOT watt/hour) which is the energy delivered by one watt of power over 3600 seconds, or 3600 joules.

- Warren

chroot

JohnDubYa,

Are you simply trying to impress upon rayjohn01 that the value of the potential is arbitrary (since you are free to select your zero anywhere you like) and only differences in potential matter?

rayjohn,

It should be clear that many people here have quite a bit more education in physics than what you got for your BSEE.

- Warren