• We’re currently investigating an issue related to the forum theme and styling that is impacting page layout and visual formatting. The problem has been identified, and we are actively working on a resolution. There is no impact to user data or functionality, this is strictly a front-end display issue. We’ll post an update once the fix has been deployed. Thanks for your patience while we get this sorted.

Holy Electrial Terms Batman

S

Stiganator

Platinum Member
Guys, I am not real learned in the ways of electronics and motors and what not, just computers. Explain to me how and what volt, amp, watt, and ohm are/do? Thanx
 
Stiganator,
I would also like to learn more about this AT THE ATOMIC LEVEL.
I think I may know but I am not sure.

Is Voltage measuring the speed of the electrons?

Is Amps the number of electrons?

Votage (speed) X Amps (numbers) = Watts (total power)?

Ohms are resistance? (block the path of the electrons and slow them down giving off heat instead)?

When the electrons travel through a conductor, do they go around the atoms in the conductor or do they replace the electrons in the atoms of the conductor and force the old electron on to the next atom etc..?
 
Stiganator -

Voltage as an analogy with a hydraulic system is quite accurately compared to water pressure. Also called EMF or electro motive force. Symbol was E, but seems to be V now.

amperes - Current, the rate of flow ( of electrons ) symbol I

Ohms - unit of electrical resistance, symbol R.

Watts - volts X amps sysmbol is W. Unit of power like horsepower or erg.

Curt Oien -

OK on most. Voltage is a potential or pressure. nothing has to move to have voltage. Current is the number of electrons past a point per unit time.

Anybody with a good link to a tutorial page - go for it
 
Voltage doesn't directly relate to electron speed. It isn't quite like water in a pipe, but sometimes the analogy gets used.

Voltage is the Potential between point A and B. The two points don't even need to be connected to have a difference in potential. The higher the difference in electrical charge, the higher the Voltage.

Current is a measurement of how many electrons per second travel through the conductor. The time factor is very important, because large amounts of electrons in short periods of time can cause a lot of heat.

Which brings up Resistance. Measured in Ohms, it is a conductor's tendency to resist the movement of electrons. Good conductors have lots of free electrons in their outer shells. Metals are a good example where they usually have only one or two electrons in an outer shell that may hold eight. So, the electrons are not tightly bound and are free to move if some Voltage potential is placed across it. Yes, Curt, the electrons do swap from atom to atom, not just weave around like cars in traffic.

When you pass current through a conductor, you must be concerned about the resisitance. The formula for calculating that heat (or wattage) is current squared times resistance. If you have 4 amps of current going through 5 ohms of resistance, you will create (4*4)*5 watts of heat, or 80 watts.

The standard formulas are:

V * I = P (voltage times current equals power) ("I" is the standard variable for current)
I2 * R = P (current squared times resistance equals power)
I * R = V (voltage divided by resistance equals current)

So, as processors use lower and lower voltages, it reduces the amount of current pushed through the circuitry, therefore it may reduce the power consumption (heat) of the processor. Of course, if they just add more transistors while reducing the voltage, the amount of current could go up because there are more current paths, therefore more heat produced.

The high voltage transmission lines that run from city to city use extremely high voltages. Since V * I = Power, by increasing the voltage, you can reduce the current and get the same amount of power transmitted from city to city. If you reduce the current, you reduce the heating of the wire, which is good because that is wasted power that never makes it to the destination. I'm talking 138,000 volts, 345,000 volts and even higher. Some lines use close to a million volts.
 
Curt Oien: When the electrons travel through a conductor, do they go around the atoms in the conductor or do they replace the electrons in the atoms of the conductor and force the old electron on to the next atom etc..?

No. In a typical copper conductor, current occurs by the movement of free electrons. They can be visualized as a swarm of free particles in the bulk of the conductor. An individual free electron is not associated with any particular copper atom. An electrical current though a wire is a slow average drift of free electrons. In a typical power circuit, the average electron speed may be a fraction of a meter per second.

I believe hole current in a P semiconductor moves more as you suggest - by a movement of electrons from atom to atom. This mechanism is intrinsically slower.
 
Just one thing, then I'll shut up.
Amperes is a measure of the movement of electric charge, not electrons, through a single point. You can have very few electrons moving very fast through that point or a large number of electrons moving through that point slowly and the measured current would be the same.
 
here is the full water example:
you have a pump that lifts water, then a bunch of tubes going all the way down to the bottom. along the way are various thigns that use the water to do something (spin wheels, etc).

the pump is the battery. it creates a difference - the height difference between top and bottom corresponds to the voltage. the amount of water lifted is the maximum amount of current (amps) available. the amount of work you can do (energy) is determined by amount of water * height it is (voltage * amps) and is a watt.

water cannot flow completely freely through the tubes due to friction, etc... this is similar to resistance, measured in ohms.

each load, such as, say, a water wheel, resists the flow of water through it, and has a height difference from its top to its bottom - this is its voltage drop.

lets say you have two loads... you can put them in one of two configurations: on top of each other, or next to each other. if they are on top of each other, each one has only half the height difference (voltage). but both have the same amount of water flowing through them (current). if you put them next to each other, both get the full height difference, but each only get half the amount of water flowing through them. in a computer,hard drives, fans, etc are next to each other, but the power supply can supply infinitely (in practice) much water at the proper height distances, so not onlyl do the devices get the whole drop, they get as much water as they need. the reason you can't power a computer off a few normal batteries is that they can only supply a trickle of water at their height difference (slightly oversimplified), so if that is shared among devices it isn't enough.

hopefully that makes sense 🙂
 
Sahakiel:

<< Amperes is a measure of the movement of electric charge, not electrons, through a single point. You can have very few electrons moving very fast through that point or a large number of electrons moving through that point slowly and the measured current would be the same. >>


Your idea that the amount of charge has a relation to the velocity of the charge is incorrect.

The smallest unit of electric charge is that carried by an electron ( - ) or a proton ( + ).
If ~6,242,200,000,000,000,000 electrons ( at any speed ) move past a point in 1 second, that is what you call 1 ampere. More rarely, it could also be protons moving in an opposite direction, say, as +ions in an electrochemical bath.

Good site hyperphysics
 
And contary to popular belief, electons move from negitive to positive. + to - is actually following the electron "holes".
 
Let's throw in another concept. Capacitors. Take two large sheets of aluminum foil and two thin, but slightly larger, sheets of plastic wrap. Layer them as Plastic-metal-plastic-metal. Now, starting a one side, carefully roll it into a tube. You have made a capacitor. If you connect a Direct Current (DC) power supply of some moderate voltage (12 volts) to each aluminum sheet, you will get a rapid inrush of current into your capacitor. Assuming there are no short-circuits from foil layer to foil layer, a charge will build up between the two layers and it will eventually reach and stabilize at the same voltage provided by the power supply. If you disconnect the power supply, the charge will remain for a long time. The better the insulating layer (the plastic, in this case), the longer the capacitor can hold a charge. If you connect something like a light bulb across the leads, the capacitor will discharge through the bulb, glowing brightly at first, then dimming as the voltage drops in rather steep curve. If you leave it connected long enough, all charge (voltage) will disappear.

I mention this because it is a case where current (electrons) will flow into something, but never actually go through it. A capacitor can continue to build a charge until it reaches a point where something inside fails, usually the insulating layer, and then it will discharge internally and perhaps even make some smoke. The insulating layer is called the dialectric and it makes or breaks how well a capacitor performs and what voltage ratings it gets. The "capacity" of a capacitor is measure in farads and is determined by the size in the foil (in square centimeters) and the thickness of the dialectric layer. The thinner the layer, the higher the farad rating (but thinner layers generally have lower maximum voltages before failure).

Now, to use the water model, a capacitor is like a balloon. If you have a 5psi water source and attach it to a balloon, the ballon will continue to expand until its internal pressure reaches 5psi, then it stops growing. If the latex is too thin, it explodes because you exceeded its "dialectric rating." So you either lower the pressure or use thicker latex, but then the balloon won't get as large (smaller farad rating). They actually use things like this in fluid systems to stabilize pressure, identical to the reason why you put capacitors in power supplies to stabilize the voltage.
 
Thank you all. 🙂

I'm learning good stuff here.
Later on, I will read this all again so it will sink in better.
EDIT: (It looks like I've got some good reading to do with that link to Hyperphysics)

The only formal electrical training I had was about 30 yrs. ago for a few months in 8th grade.
I asked the teacher some of these questions and he had no clue.
He was irritated with me for asking how this stuff worked and just wanted us to memorize the formulas.
He said they worked because they do and if I just memorized the formulas I would understand electricity. 😕

PM had written something on overclocking a while ago and from what I understood, if you raise the voltage or make the conductor colder, the electrical charge will get to its destination quicker.
Does colder = less resistance because the individual atoms in the conductor are not bouncing around and getting in the way of the electrons as much?
Because voltage is like water pressure, as it increases, do the electrons move more quickly through the conductor?
Does increased voltage cause more heat in the conductor because the faster moving electrons bump the conductor?s atoms harder causing them to wiggle more?

Thanks again. 🙂
 
On the "electricity moves from+ to -" front. I actually argued this with my physics teacher in high school. His argument: "it moves from a higher potential to a lower" (while we're on that topic, where's the top of the world?).

Some other terms:
Inductance: electrical value associated with the electromagnetic charactaristics of a part when electricity is flowing through it. (in the sense that it doesn't like a change in amperage). Typically measured in "Henrys"

Capacitance: electrical value associated with the charactaristic of a part when there is a voltage difference between two parts of itself, or a part of itself and something else, seperated by an insulator. (resists a voltage change). Typically measured in "Farads"

Impedance: Effective resistance of a circuit once inductance and/or capacitance is taken into account. Typically measured in "Ohms"

An example of impedance is a transformer w/ 1 Ohm of resistance on a 120VAC line. This isn't an uncommon resistance for a transformer. Ohms law would state that this has 120A of current (which would be massive). However it's likely to have 12 Ohms of impedance due to inductance at 60Hz. Suddenly it's down to a realistic 10A.
 
Evadman is right, it is called "hole flow" but you have to relate this to what he is trying to learn. In Physics they teach differently then in electronics courses and follow electron flow instead of the "holes" both are right just a different way of learning. Also in the electronics area, Voltage is more commonly referred to as "E" not "V", it all just depends on what classes or books you are reading. Another thing that you have to account in for is that depending on the frequency of what you are sending, the higher the frequency the more resistance per unit of length, but this has more to do with the transmission of RF.
 
one more thing to throw in is an inductor... it is a coil of wire. basically, it tries to keep the current flowing through it constant. so, if you connect a light bulb in series with an inductor in a simple circuit, the light bulb would start to glow slowly as the amount of current rises. this is because the inductor creates a magnetic field with the change in current (from 0 to nonzero). the current will slowly increase and the light will get brighter until the current reaches the maximum amount. at this point, the current will be constant again and therefore the inductor won't really be doing anything. if you then remove the battery and instantly replace it with a wire, the inductor will keep the light glowing (for a very short time) as its magnetic field is converted back into current.

I'm trying to think up a water analogy for this... maybe if you take a really heavy (frictionless) fan and put it in the pipe. as water starts to flow, it will be strongly resisted since it has to spin up the fan. as the fan spins to the max speed, it effectively disappears and water flows through it normally. when you stop the pump though, the fan will continue to spin due to its inertia for a while and prevent the current from completely stopping.

Another analogy for an inductor would be a flywheel - it likes to hold its speed and resists change.

A capacitor likes to hold its voltage constant - it will absorb small spikes and fill small drops of anything in parallel with it.
 
I tried to leave "hole" flow out of the equation since it is a semi-conductor event. In standard metallic conductors, the quantity of free and readily movable electrons make hole flow unnecessary. I choose to ignore it most of the time. Unless you are a quantum physicist, you can practically ignore hole flow.

Back to some of Curt's new questions:

As conductors get colder, their resistance goes down. You can use the variation of resistance with temperature to make extremely accurate temperature sensors. (This isn't always true, though. There are a few materials, metal alloys and semi-conductors, that exhibit backwards behavior over parts of the temperature spectrum.)

At or near absolute zero, resistance goes away as atomic motion ceases. Electrons never stop orbiting and moving, but the protons and neutrons come to a stop, so I suppose they stop interfering with electron movement. Some alloys exhibit near zero resistance well above absolute zero, but so far they are very expensive, so not widely used. Room temperature super-conductors would make a big difference to the world's energy producers, so they keep looking.

Sometimes, as the high temperature makes the resistance of a conductor go up, that causes the conductor to produce more heat from the current flow, which then makes it hotter, so resistance goes up again and so it produces more heat, etc., etc., until it just melts and stops the flow of current. I've seen overloaded extension cords do this.

Ctho, your water analogy for an inductor would be like a water wheel with a large flywheel attached. It would resist the flow of water until it reached full speed, then, even if the water flow stopped, it would continue trying to pump water as it spun down.
 
In the real world of hydraulics, one doesn't have to search very hard for an inductance analogy. "Water hammer" is the very common effect of the momentum of a moving fluid in a pipe; it is the inductance in the system. Water hammer can be quite destructive to valves and is a real nuisance. The effect must be dealt with whether it is the Space Shuttle main flight controls or ordinary plumbing.

For example, any properly plumbed house will have a stand pipe in the wall near any faucet valve. The stand pipe is the snubber "capacitor" which reduces pressure spikes ( voltage spikes ) caused by suddenly stopping ( switching off ) the flow ( current ) in the pipe ( inductor ). A stand pipe is a vertical pipe closed at the top. The trapped air in it compresses to temporarily store energy much as a capacitor would store energy in an equivalent electrical circuit.

Didn't know that bathroom sink was so dynamic, did you? 🙂

I should say that these comparisons of electrical quantities to other more familiar things like water in a pipe are great for conceptualizing electrical circuits. But, there is another interesting side to this. After a person then becomes very handy with all things electrical, it is easy to put the process in reverse. Say, you want to analyze vibration in a crankshaft, something that must usually be done very thoroughly. One of the easiest and natural ways to do this then is to convert the mechanical quantities of the crankshaft to electrical ones - convert the crankshaft to a modest sized circuit and analyze it for frequency response, impedance , whatever. All of the tools for circuit analyses are available then for a very broad range of applications.

So, it can work both ways and that's good.
 
I did not see where anyone wrote down Ohms law. This is the fundamental relationship defining simple DC circuits.

E = I R

This can be read as a voltage, E, across a resistance, R, causes a current I.

Also there are several ways of writting the power consumption of a simple circiut

P = I E (Power = current * Voltage) given above OR
P = I^2 R (need this to get the right wattage of resistor)
P= (E^2)/R not the most commonly used.

The power relationships can be gotten from each other by applying Ohms law.

 


<< Guys, I am not real learned in the ways of electronics and motors and what not, just computers. Explain to me how and what volt, amp, watt, and ohm are/do? Thanx >>



Compared to water:

volt=pressure

amp=amount of flow

ohm=resistance

I don't know how watt relates so I'll have to explain. Watt is basically a work over time and the very basics is volt x amp. It gets more complicated on AC circuits.

 
Highwire. This goes right back at ya (from the link you provided)
"Electric current is the rate of charge flow past a given point in an electric circuit, measured in coulombs/second which is named amperes"

Amperes is dependent on charge, not electrons. Electrons happen to have a fixed charge, so most people think that amperes measures electrons per second.
Taking that into account, assume we have a plastic comb that carries an electric charge. You pass it through a fixed point in space at a certain speed, you get a certain measurement of current in amperes. You pass it through that same point at twice the speed, and you get twice the amperes. Amperes is measured by charge, not electrons. It is not confined to the molecular level.
Then, there's also the problem of having both anions and cations move past that one point. Example: One electron moves past point A in one direction, then one proton follows and passes point A in the same direction. In this example, the measured current is 0. Zip, zilch, nada, nothing, despite the fact that an electron has passed through the point.
So you see, treating amperes as a measurement of electron flow is fine and dandy for beginning physics study but I think it's best to always remember it's charge, not electrons. It'll save the confusion and headache when working with flowing cations.
 
Sahakiel -


<< Highwire. This goes right back at ya (from the link you provided)
"Electric current is the rate of charge flow past a given point in an electric circuit, measured in coulombs/second which is named amperes"
Amperes is dependent on charge, not electrons. Electrons happen to have a fixed charge, so most people think that amperes measures electrons per second. >>



Can an electrical charge exist and not involve the presence or absence of an electron? I don't think so, at lease not outside of a nucleus and its strange zoo of subatomics.
Maybe I am missing something, but I don't know how to get a charge on something without it involving electrons. Do you? It is fundamental. If I want to charge something negatively, I just put electrons on it. If I want to charge something positively, I must take electrons away. The remaining protons give it a positive charge. If I rub a glass rod with fur, I am playing with electrons, removing them here, adding them there.

Any charge is some whole number multiple of the charge of one electron and the charge is there only because of the presence or absence of ELECTRONS there. Electric charge only comes in electron sized units, nothing smaller, nothing bigger. This applies also to all ions, protons and, err, it's a small list. The only basic things that have electric charge are electrons and protons outside of the zoo, that is. Ions are atoms with added or absent electrons. Electrical current involves the movement of mobil charges. So, you can count these electron sized units of charge carried past a given point, both positive and negative charges in positive and negative directions, take the algebraic sum and that is an electrical current.

By the way, a coulomb is the charge of a definite large number of electrons, the number I gave before - 1 amp second of current. So, amperes DOES measure electrons per second one way or the other. For example, a chromium ion in a plating bath can not travel up the wire to the ammeter. It meets an electron flowing in the opposite direction and forms a neutral chromium atom. So, you can bet you booty you are measuring electron flow.



<< Taking that into account, assume we have a plastic comb that carries an electric charge. You pass it through a fixed point in space at a certain speed, you get a certain measurement of current in amperes. You pass it through that same point at twice the speed, and you get twice the amperes. >>


Again, current is the amount of charge per unit time moving past a point. It has NOTHING to do with the velocity of the charge carrier. You may be confounding the words RATE ( few / many per unit time )and VELOCITY ( slow / fast )( distance per unit time ).

In the example you contrived, if you put a fixed density of charges on a comb and move it past a point, the rate and velocity will be CORRELATED, but again, only the rate is important. If you place the same total charge on a tiny comb as on a very large comb and move each comb past a point in one second, guess what? The slower moving charges on the tiny comb produce the same current as the faster charges on the larger, faster moving comb. Measuring current is really just a counting process, like counting the number of cars that past a toll booth in an hour. No radar gun needed.
 
You guys are good. 🙂
I'm actually finally really understanding electricity.

You have spent so much time helping me that I almost hate to ask more questions.
But you guys seem to really know your stuff and I'm not going to let this opportunity pass.
I want to understand conductors too.

At the atomic level:
What makes a good conductor?
Why can electrons flow through some things and not others?
Does lightning need air/Without using something like an electron gun, can electricity jump across a vacuum?
Who should I make the check out to for this education?
Is it true that deionized water is not a conductor but ionized is? If so,why?

Thank you all again. 🙂
 
Raw hotdog==good conductor
Cooked hotdog==not so good conductor

In my physics class we used this principle to cook hotdogs w/ 120VAC and use an ammeter to tell when they're done (10A raw, quick drop to 1A when done)
 
What is a conductor and what isn't? What is a semi-conductor? wow

First you have to look at an chart of the elements (the Periodic Chart of the Elements). The arrangement of the elements have to do with the number of electrons in their outmost shell. Remember, if an outer electron shell is full, the atom is considered inert. Inert elements don't generally conduct, except when ionized, but I'll get to that.

The elements in the middle section of the tables are metals. They are called metals because their particular combination of protons, neutrons and electrons give them metallic properties, such as hardness, shiny, usually silvery (or what is called a "metallic" look) and they are conductive. They are conductive because their outer shell of electrons are loosely bound to the nucleus of the atom.

Farther to the right of the chart, you get into the opposite materials. The Insulators. They don't conduct, even though they may be solid. Their outer electron shells are almost full and are not free to travel. If you put enough voltage across them, they will conduct, but it is usually a destructive process because you are actually ripping the electrons out of their orbits and they don't like it.

Vacuum is a good, but not a great, insulator. For instance, a bolt of "lightning" can definitely across a gap, but it takes very, very high voltages. The vacuum tube is a perfect example that electrons (no "hole flow" here) can cross a vacuum. In a vacuum tube, you electrically heat a metal until it gets so hot that its electrons are liberated into a cloud around it. Then you put a high positive charge on a grid or plate a few centimeters away and the electrons will move, at great speed, and hit that plate. If you are reading this on a CRT monitor right now, the electrons have made the trip. The above vacuum tube example makes a simple diode. The current can only flow from the heated metal end, the cathode, to the positive end, the anode. To turn a vacuum tube into an amplifier just takes the addition of one or more control grids to manipulate electron flow.

Ions are where it gets fuzzy. An ion is merely an atom with extra electrons or missing electrons from its normal, neutral state. Some atoms, like Chlorine, will dissolve in water and "ionize" by taking an electron from some available molecule. This gives them a negative charge of 1. Sodium does just the opposite and will give up an electron to something, becoming positively charged. When you dissolve Salt in water, the sodium and chlorine atoms disassociate and form their appropriate ions. When you apply a voltage across that solution, current will flow by the movement of ions through the water.

An earlier post discussed the movement of "charges" rather than electrons, and this illustrates that point. It isn't really electrons moving, but ions.

Another type of ion is caused by heat or electrical excitation. The most common example is the Neon sign or tube. Fill a long glass tube with Neon or Argon or Krypton gas (they are normally inert elements) and put a few thousand volt potential from one end to the other and the gas will ionize and begin to conduct electricity. While ionized, it will give you that characteristic colorful light we call "neon." The light comes from the excitation of the electrons in the outer shell. They will actually jump to a higher orbit and then drop back down, in the process the give off a photon (light).
 
You must log in or register to reply here.

TRENDING THREADS

Back
Top