Voltage. What is it really?

sophiecentaur

"real" answer?
you mean 'another' answer, perhaps.

sophiecentaur

It's difficult to relate the Fields in a circuit to Voltages. Where do you choose to imagine the two points to be in order to calculate the Volts per Metre? A circuit could be a 10km loop or a 5mm loop and the Volts would be the same. It would have to depend upon the separation of the terminals connecting the battery perhaps??? This is why we use Potential all the time and not Field. The Joules per Coulomb are not dependent on any fields that may be present around the circuit.

jartsa

I have improved my answer #17 by deleting lot of quoted text. Now you see I just added the length, which surely is an improvement.

How does an ordinary volt meter measure the voltage between the floor and the ceiling (a large capacitor) ?

Well, the connecting wires are of certain length and the same field that goes through the air, goes through the wires. Every electron in the wires is pulling or pushing the few electrons in the resistor through the resistor that is inside the volt meter.

The volt meter measures the leakage of electrons, caused by the pressure of the stack of electrons in the wire.

Aero51

Why don't you share what you feel sufficient answer? In your first post you state that a voltage is a J/C, which is true, but doesn't really provide insight as to what a volt is in physical terms. After all, a Joule and a Coulomb are just units of length mass time and charge.

Granted I cant answer my own question with great accuracy as I am not an electrical engineer or a physicist who's studied electricity. So how would you describe a volt in terms of physical phenomena?

davenn

nope, sorry, that is even more confusing .... left me shaking my head
would you like to try again ?
.... measures the leakage of what electrons ?
you seem to be hung up on long wires .... forget the long wires, as sophiecentaur, hinted at
we dont have them in a small electronic circuit.
Get Back to explaining the definition of voltage potential difference across the terminals of say a battery
Dont forget a Voltmeter is just a Ammeter with series rather than shunt resistance ;)


Dave

Ratch

fydp014,

So it is measured in J/C. What does that tell you? It should tell you that voltage is the energy density of the charge. Let's take a charged carrier like an electron, for instance. All electrons have the smallest quantum of negative charge. Now because they all have the same charge, they don't like to get close together. In fact, it takes energy to gather them into a volume. The more electrons are crammed into a volume, and the smaller the volume, the higher the energy density/charge (voltage) is. These electrons are always looking for a place where the energy density/charge is lower so they can spread out more. For a wire with a higher voltage at one end, they are going to travel down the conduction path to the lower energy density/charge (voltage). During their travel, they will encounter collisions with the ionic cores of the wire, which will increase the temperature of the wire and dissipate heat. So they will arrive at the end of the wire with less energy and a lower energy density/charge. That explains "voltage drop".

Now ask questions.

Ratch

jartsa

OK now post #20 should be correct, after some editing.

ImaLooser

"You just can't train nose hairs." --- Don Martin.

mikelepore

This is an analogy I use. Suppose I ask you to carry ten rocks. That tells you how many. Then I tell you that you need to carry them to the top of a mountain. That tells you how much work you must do per rock. Similarly, current is how much charge is being moved per unit of time, and voltage is the work done per unit of charge.

banerjeerupak

I think the box being pushed analogy makes the most sense. I passed through school and then college without ever realizing how cool this analogy was. Drakkith gave a great thing to remember about voltage!!

sophiecentaur

The word "insight" is a bit like 'motherhood' and no one likes to question it but what are we actually after?
My "sufficient answer" to the whole problem is to use the Definition (V=J/C). This is not a cop out; it Works when you need to predict what will happen in a given situation.

I am just acknowledging that the feeling that people 'need' before they allow themselves to 'understand' things is very little more than Familiarity. Use something enough times and you treat it as second nature. A new piece of what we call understanding is no more than using a new combination of familiar ideas in a way that satisfies us that we "now understand it". We have managed to pigeonhole it amongst the things we feel we are familiar with. (If you are really after improving your understanding, you use these pigeonholes as temporary storage, only - a Scientist is always emptying holes and replacing their contents with an improved version.)
Humans have spent hundreds of years in developing a mathematical system to describe / analyse / predict natural phenomena so why not be prepared to use it? The mathematical descriptions used in Physics are every bit as 'real' as the dodgy analogies that people seem to hang all their hopes on. In my view, it is pointless and fruitless to ask for a 'physically meaningful' explanation for anything but the most concrete phenomena (and even then, the explanation is just not that simple).

I have frequently made the point that many of the posts on these forums (some of mine included, of course) merely serve to confuse the uninitiated. The 'worst' ones are of the rambling, speculative kind which use none of the accepted ideas or the mathematical approach. Unless someone challenges them, they appear just as attractive as the more accepted views and can seriously damage someone's potential learning process.