What Is Electricity: Exploring Its Nature

[Per Oni]

Yes but the electrons never actually leave the copper wire's atoms! Othewise we'd end up with a bunch of electronless atoms. What then "feeds" an electric device? Charge?

Never is a very short time, and not quite right.
In a short time called "relaxation time" there's a slight imbalance in which one
electron will have flowed a certain distance before being replaced by the one behind.

 

[mikelepore]

Ok that sounds wrong, but how would you correct my explanation?

mopc, if you delve now into the subject of how motors and generators work, that's like skipping a hundred pages in the textbook before your real solid about the previous chapter.

The kind of questions you are asking indicate that you're not completely familiar with the concepts of potential energy, and this is where an analogy with gravity is helpful.

In a gravitational field, if you lift a mass to a higher altitude, say, you carry a rock to the top of a mountain, you're giving it potential energy, because when you release it then it will fall back down. You did work to displace it in the non-spontaneous direction, upward, and when it's released it will respond to a field that exists in its vicinity of space, gravity, by accelerating in its spontaneous direction, downward.

Electricity is very similar, but now it's an electric field instead of a gravitational field. If you move a positive charge closer to the positive terminal, or move a negative charge closer to the negative terminal, you're doing work on it to compel it to go in the direction that it's naturally repelled from. This gives it potential energy. Then you will observe that it moves spontaneously the other way, a positive charge moving toward the negative terminal, or a negative charge moving toward the positive terminal.

A battery has a chemical reaction that continuously puts out electrons in one place and takes in electrons in another place, causing regions of space that have relatively higher and lower potentials to be maintained. What a battery is doing is like a person doing work to carry a bunch of rocks up to the top of a mountain, and allowing them to roll back down, continuously putting things in a location where they will acquire potential energy, the tendency to start moving spontaneously in the opposite way.

You also asked about the meaning of the word "power". To continue the analogy with gravity:

To get to the units of energy per unit time, which we call power, simple reasoning will tell you that you will have two variables to multiply. One variable is current, and that's analogous to how many buckets of rocks you have to carry in a given amount of time. The other variable is voltage, which is like the fact that you're carrying those buckets of rocks up a steep slope instead of carrying them on level ground. You will have to multiply these two things. Therefore, power means current multiplied by voltage.

Numerical example with units: If 5 amperes of current flow, which means the movement of charged particles at rate of 5 coulombs per second, and if these charged particles are being displaced across a potential difference of 10 volts, then power is being delivered at a rate of 50 watts, which means electrical energy is supplied at a rate of 50 joules per second.

These are still not enough fundamentals to explain how motors and generators work, which requires a discussion of additional effects, the magnetic field and magnetic forces.

 

[mopc]

"Numerical example with units: If 5 amperes of current flow, which means the movement of charged particles at rate of 5 coulombs per second, and if these charged particles are being displaced across a potential difference of 10 volts, then power is being delivered at a rate of 50 watts, which means electrical energy is supplied at a rate of 50 joules per second."

This paragraph is close to what I want to know. But what is a potential difference of 10 volts? Oh I researched, potential difference is merely another name for voltage. Voltage is like electric pressure. So apparently voltage is what happens when you have a difference between two lumps of matter with different electric charges. One electric charge will flow to where it is attrached, and vice-versa. Like my diagram full of +'s and -'s.

Voltage is the intensity of that flow. Right? Damn.

 

[mikelepore]

Your question about what voltage (that is, potential difference) really means, answer: potential energy per unit of charge.

This would be the simplest derivation, algebra instead of calculus.

Equation 1: electrical potential energy is equal in magnitude to work W, which refers to a force F acting through a distance d: W=Fd

Equation 2: an electric field E acting on a charge q will cause it to experience a force F: F=qE

Substituting eq. 2 into eq. 1: W=qEd

So the product Ed is the work done per unit charge, and after you multiply that Ed by charge q you will have an expression for work or energy.

Define the potential difference V to be the term Ed, that is, the work per unit charge.

V=Ed
W=qV

To move a charge q across a potential difference of V, you will do work in the amount of (and change its potential energy in the amount of) W=qV.

When a charge of 3 coulombs is moved across a potential difference of 9 volts (that is, 9 joules per coulomb), the work done, and the change of its potential energy, is 27 joules.

But work done by what or by whom?

If the charge moves in the spontaneously attracted direction, say, negative charge approaching the positive pole, we would say the electric field performed 27 J of work on the charge.

If an active device, a supplied energy source, such as a battery, moves the charge in the non-spontaneous direction, negative charge approaching the negative pole, we would say the the energy source did the work on the charge, and did work against the electric field.

I'm an electrical engineer and there are sometimes minor difference in terminology between what I call things and what the physics community calls them.

 

[cabraham]

That's stupid. You never learned from your classmates when you had your education? Reading a non-professional's take on subjects that are usually handled by experts(who most often use the very same explanations as one another) can be very refreshing. I love to see a crazy new solution to problems.

Great read! It brought up many questions that I've never thought of before.

What are his erroneous facts in particular? I'm asking of interest and not to disprove your point.

Sticking with peer-reviewed info is STUPID, you say. I say not.

His erroneous facts cover most of field theory. He has no clue how conservation of energy applies with fields. I've exchanged emails with him. If you want, I could forward them to you. He makes assumptions not valid. His semiconductor physics, esp w/ transistors, flies in the face of every transistor maker in the world. The fallacy is in his misunderstanding of fields in particular.

Claude

 

[user111_23]

Electricity is about the subatomic particles in the atom-such as the electron and the proton-and their attraction and repulsion. Electricity is a property of matter.

 

[GRB 080319B]

Sticking with peer-reviewed info is STUPID, you say. I say not.

His erroneous facts cover most of field theory. He has no clue how conservation of energy applies with fields. I've exchanged emails with him. If you want, I could forward them to you. He makes assumptions not valid. His semiconductor physics, esp w/ transistors, flies in the face of every transistor maker in the world. The fallacy is in his misunderstanding of fields in particular.

Claude

I apologize for giving a bad source. I didn't know that his information was fallacious and not peer-reviewed. Thanks for bringing this to my attention.