Ohms, Amps, Watts, Coulombs, Charge ... What the hell is Electricity and Magnetism ?

Topic split from the solar panels thread here

- Auditor

Auditor #9 wrote:

Ok I'm understanding most of that in a very shallow way at least - something I wouldn't have understood at all last week.

My problem is connecting these feckers up now and it might answer the trickle questions for me if it starts to work.

It's really like a gearbox then is it? that's a cool way of looking at it...

Funnily enough Audi, it is a cool way of looking at it.

If you try to remember at all times that power = volts X amps then you can't go wrong.

Imagine a flywheel on an engine. A big balanced disk of steel with shiny teeth.

When does this disk have more power : at 600rpm or 1200rpm?

Though in engines they call it torque.

Electrical power is the same as any other power. It is the rate of use of energy.

Energy is measured in Joules. Thats the amount of energy to move 1 Newton through 1Meter. Or whatever

Power is the rate of burn, Joules per second. Its the speed of the peddals on yer bike !

Now another name for Joules per second is Watts !

See where this is going ?

EvotingMachine0197 wrote:

See where this is going ?

heat and energy and electricity are all the same stuff or are very closely related ...

Yeah this is interesting because before we talked about hydrogen and the energy value of it and it's all related isn't it?

What about calories and btus? Are they different bodily energies - calories being biological and btu's being heat?

Audi, it is all related. The law of conservation of energy.

After that, I only know about the electrical bit.

For instance, did you know that most electrical definitions don't really have a definition ?

EvotingMachine0197 wrote:

Audi, it is all related. The law of conservation of energy.

After that, I only know about the electrical bit.

For instance, did you know that most electrical definitions don't really have a definition ?

Most electrical definitions don't have a definition ? I didn't really know that but I sort of did too - all the definitions are either references to each other but they are not circular they ultimately refer to force and more ultimately to charge.

No one knows what is charge.

Auditor #9 wrote:

EvotingMachine0197 wrote:

Audi, it is all related. The law of conservation of energy.

After that, I only know about the electrical bit.

For instance, did you know that most electrical definitions don't really have a definition ?

Most electrical definitions don't have a definition ? I didn't really know that but I sort of did too - all the definitions are either references to each other but they are not circular they ultimately refer to force and more ultimately to charge.

No one knows what is charge.

No one knows what magnetism is either. And yet charge and magnetism are sort of related.

Current (the amp) is sometimes defined in terms of the magnetic force between two infinitely long conductors placed 1 meter apart in a vacuum. Obviously an impossible experiment to set up.

However current can also be defind in terms of charge, ie. the number of coulombs (charge) per second in a cable. So I think it is reasonable to say that charge is a count of electrons, whether they are moving (current) or not moving (static).

In electronics, everything can be defined as everything. Probably applies to everything else too. I bet I could define anything in terms of pints of guinness...

EvotingMachine0197 wrote:

Auditor #9 wrote:

EvotingMachine0197 wrote:

Audi, it is all related. The law of conservation of energy.

After that, I only know about the electrical bit.

For instance, did you know that most electrical definitions don't really have a definition ?

Most electrical definitions don't have a definition ? I didn't really know that but I sort of did too - all the definitions are either references to each other but they are not circular they ultimately refer to force and more ultimately to charge.

No one knows what is charge.

No one knows what magnetism is either. And yet charge and magnetism are sort of related.

Current (the amp) is sometimes defined in terms of the magnetic force between two infinitely long conductors placed 1 meter apart in a vacuum. Obviously an impossible experiment to set up.

However current can also be defind in terms of charge, ie. the number of coulombs (charge) per second in a cable. So I think it is reasonable to say that charge is a count of electrons, whether they are moving (current) or not moving (static).

In electronics, everything can be defined as everything. Probably applies to everything else too. I bet I could define anything in terms of pints of guinness...

I love that one about the Amps - have you any more? Isn't the Coulomb the force between two electrons with some distance between them hanging off a clothes line probably in a vacuum too? The Coulomb equation was always suspiciously like Newton's inverse-square law for gravity to me.

Isn't magnetism the repulsion/attraction of positive and negative charge? And isn't a magnet an ordered set of tiny electrical currents that all combined create the thin we know of as a magnet. The current doesn't flow into you and kill you either from a magnet. Is it possible to get electrocuted by one?

Why is charge positive and negative? Have we any better names for positive and negative - but that's nuclear physics I suppose. Not that I've been thinking about it too long but is there such thing as a flow of protons? Or are they too hard to get out of a piece of copper.

i think we're off topic but ah we'll get back to it eventually.

No, magnets are not electrical and don't have charge per se. You could apply a static charge to one, but it's still just a magnet.

The interaction between electric currents and magnetic fields is the mad bit. Magnetic fields can induce current, and current can generate magnetic fields. And fields can induce other fields. This is the stuff that gives us transformers, motors and generators.

Quote :

Why is charge positive and negative? Have we any better names for
positive and negative - but that's nuclear physics I suppose. Not that
I've been thinking about it too long but is there such thing as a flow
of protons? Or are they too hard to get out of a piece of copper.

This would be more like atomic physics than nuclear physics. Charge is positive if electrons are missing from the atom. Negative if there are extra electrons. Protons don't move about because they are 'stuck' in the nucleus. Electrons are very mobile and fly all over the gaff. Do you remember anything about valence bands and all that ?

LEDs use this mobile electron principle to convert current into light quite efficiently.

It is well off topic now. Should we split it out ?

EvotingMachine0197 wrote:

No, magnets are not electrical and don't have charge per se. You could apply a static charge to one, but it's still just a magnet.

Isn't electromagnetism the theory that one is an aspect of the other? http://en.wikipedia.org/wiki/Electromagnetism

Quote :

The interaction between electric currents and magnetic fields is the mad bit. Magnetic fields can induce current, and current can generate magnetic fields. And fields can induce other fields. This is the stuff that gives us transformers, motors and generators.

I'd kind of forgotten that stuff - is this where the Tesla coil comes in and solenoids?

Quote :

Why is charge positive and negative? Have we any better names for
positive and negative - but that's nuclear physics I suppose. Not that
I've been thinking about it too long but is there such thing as a flow
of protons? Or are they too hard to get out of a piece of copper.

They should make up a new set of names for 'positive' and 'negative' as it doesn't say anything about the nature of charge anymore, just that one is the opposite of the other.

Quote :

This would be more like atomic physics than nuclear physics. Charge is positive if electrons are missing from the atom. Negative if there are extra electrons. Protons don't move about because they are 'stuck' in the nucleus. Electrons are very mobile and fly all over the gaff. Do you remember anything about valence bands and all that ?

Valence bonds are the grammar of chemistry is that right? There are 8 electrons hanging around the second or third shells but there doesn't have to be. They like it that there is 8 there though. If one atom has 6 there and another has 2 then they'll combine I think. Carbon is good for it because there are lots of different shells and I think the last shell has 6.

Quote :

LEDs use this mobile electron principle to convert current into light quite efficiently.

It is well off topic now. Should we split it out ?

Light emitting diodes. Other bulbs use a heated coil of wire or a gas - the LED will become standard one day soon we hope. They say changing all the traffic lights in England to LEDs could mean closing down a few nuclear power stations.

Ah all nations could be machine based nations someday. What'll you call the new thread?

(all the above information could be completely wrong, even wikipedia)

Wikipedia has this to say about someone called C. F. du Fay - ever heard of him? He was one of the boys who started to take a close look at what electricity was and how it acted and behaved. Interestingly he didn't use the terms 'positive' and 'negative' but other words which instead reflected the types of material wherein he observed the electrical and static effects.

Quote :

He discovered the existence of two types of electricity and named them "vitreous" and "resinous" (later known as positive and negative charge respectively.) He noted the difference between conductors and insulators, calling them 'electrics' and 'non-electrics' for their ability to produce contact electrification. He also discovered that alike-charged objects would repel each other and that unlike-charged objects attract.He also disproved certain misconceptions regarding electric charge, such as that of Dr. Stephen Gray who believed that electric properties of a body depended on its colour. Du Fay's observations on electricity were reported in a paper written in December of 1733 and printed in Volume 38 of the Philosophical Transactions of the Royal Society in 1734.

http://en.wikipedia.org/wiki/C._F._du_Fay

Here's* a good collection of pdf textbooks on electricity and electronics.

I think the water analogy is always a good way to start wrt to conceptualising how electricity works.

*
http://openbookproject.net//electricCircuits/

Looked at from the bottom up:

1. Electron - it's got a charge (-ve), but assuming nothing whatsoever is happening, it just sits there, being charged. Well done the electron.

2. "Static electricity" - buildup of charge. So, for example, lots of electrons all together. Again, all else being equal, this will just sit there doing nothing.

3. Current - charges in motion. So, for example, a load of electrons flowing down a wire. 1 amp = 6.242x10^18 electrons per second.

4. Voltage - charge difference between two points. Effectively, the gradient along which charge flows.

5. Power = current x voltage. As Pax says, the water analogy is a good one. The current is the "stream", and the voltage is the "slope". Say you want to move the blockage in a pipe. If you've only got a thin trickle of water, you need a lot of slope to get it to do anything. If you've got a hell of a lot of water, you don't need much slope.

6. Resistance - anything that impedes the flow of current. The blockage in the pipe in 5 can be thought of as offering resistance - the pipe is the conductor. The work that the electricity does in overcoming resistance can be turned into heat and/or light etc, depending on the properties of the material involved. There's also always a certain amount of resistance in a normal conductor, resulting from the atoms jiggling about and getting in the way of the electrons - cool any material to absolute zero and its resistance drops to zero, because the atoms stop moving.

7. Conductor - something along which charge can flow. Usually, this means it has electrons that are free to move, which in turn depends on the atomic structure.

8. Atoms - electrons bound to a nucleus of protons and neutrons. There are stable configurations, and less stable configurations - full orbitals are good, full 'shells' best (shells are sets of orbitals, orbitals are distances from the nucleus which electrons can occupy - strictly, they're probability wave functions).

Innermost 'shell' takes 2 electrons in what's called a 1s orbital. The only elements that have structures that simple are hydrogen and helium, with 1 and 2 electrons respectively. Helium, having 2 electrons, has a full set of shell 1 electrons, and is a totally unreactive gas. Next shell up has 2 s orbitals, and 6 p orbitals - when that's completely full, you've got Neon, another unreactive gas.

The outermost orbitals of the "Transition Metals" are d orbitals. The nice thing about these is that the electrons are loosely bound - which means they're able to move around, and carry current. The good ordinary conductors, by and large, are thus transition metals like copper and gold.

9. So, apply a charge difference to two ends of a wire made of a transition metal like copper, and the electrons will move. Voila, current.

10. Magnetism - moving charges generate magnetic fields, and vice versa. Every electron, because of its spin, is a tiny magnet. 'Static' magnets are the result of lining up these spins, and/or the spins of certain atomic orbitals. Strictly speaking, electricity and magnetism are simply aspects of a single electromagnetic force - the electric and magnetic effects being at right angles to each other.

Ibis and Pax thanks for your links and posts. I've been reading a little through your link Pax and find it's nice and simple for the likes of me, building the information up gradually as though he was talking to a child. Suits me down to the ground.

I've been digging around a bit more too for more details on how the different elements of electricity can be defined and described and I found another good simple site, of which I'm reading the voltage bit at the moment.

http://amasci.com/miscon/voltage.html

Auditor #9 wrote:

http://amasci.com/miscon/voltage.html

I like that article. Remember though that mechanical analogies for electricity work to some degree but eventually break down on detailed scrutiny.