Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: rpcrazy on 30/08/2007 11:49:17
-
I'm not a physicist( :P ). But I believe in common knowledge of ALL things for ALL people. Granted some people may not be able to understand some things and I except that.
I wanted to know what electricity was so i've spent the last 5 or 6 hours researching on line. And all i've learned (re-learned) is our language is ridiculously limited and scientists need to wisen on the words they use for things, i guess.
As such, here's what i've pretty found out, and I was wondering if it were true and if you could simplify anymore if it ISN'T true. If this forum is for people already in physics or something like that than forgive me, i know not what I do.
-Electricity is a term used to explain a RANDOM occurence of phenamena that happens when a series of activities occur involving electrons and the invisible energy it produces...?
-In an electrical circuit in a generator for home power, the number of electrons that are moving is called the amperage or the CURRENT(?), and it is measured in Amps. The sort of pressure(magnetic force?) pushing the electrons along is called the voltage and is measured in Volts. One amp is the number of electrons moving and that amp physically means that 6.24 x 10 to the 18th power (i think that's right) electrons move through a wire every second, and the voltage is the amount of pressure behind those electrons. That 6.24 x 10 ~ 18th number is a quantized measurement, meaning to standardize the measurement(?).
-I HAVE NO CLUE why the magnetic force pushes electrons ONLY(or does it?) or why a magnetic field is created adjacent to the electric current.
So basically the term "electricity" is incorrect by definition and electric currents are (excited? what excites them again?) electrons in movement to the closest path to the ground right? and there you go.
-
Firstly, while we do have some good scientists on this site, let me assure you that the vast majority of people here are mere laymen with an interest in science.
As for the question you ask.
Electric charge is a basic force of nature, just like gravity is a force of nature. The difference between the two is that while gravity is a force that is created by all matter in the universe, and causes all other matter in the universe to be attracted to it (i.e. everything pulls on everything else), not all matter has electric charge, and electric charge can push things away as well as pulling things together (two objects with the same charge will be pushed apart, while two objects with opposite charges will be pulled together).
The primary sources of electric charge that we encounter in our everyday lives are the electrons around the outside of atoms (which have an electric charge that we arbitrarily label as a negative charge) and the protons within the nucleus of the atom (which we arbitrarily label as positive charge). It is the opposite charges of electrons and protons that keep them tied together in the atom.
A simple example of the force of this charge is when you rub some materials together (e.g. nylon on wool), some of the electrons get rubbed off one material and onto the other, thus causing one material to have a slight excess of electrons, and the other to have a deficit of electrons, and so the one with an excess of electrons will also have an excess of negative charge, and the one a deficit of electrons will have an excess of positive charge, and since the two materials now have opposite charges, they will be pulled together.
When you are talking about voltage, what you are actually talking about is the attractive force between two objects of opposite charge. This depends on two factors - the amount of negative or positive charge the objects hold, and the distance between between the objects (it also depends on the material between the objects, but that is a more complex art of the issue, so I will deal with the easier bits right now). If the objects have more charge (e.g. they have a greater excess or deficit of electrons) then the voltage between them will increase. On the other hand, the further apart you pull the objects, the less will be the force between them, so the voltage will decrease (if you rub wool and nylon together, and then move the two objects to opposite sides of the room, they will have no discernible pull upon each other; but if they are close together, they will pull each other more strongly).
When two objects have a voltage applied between them (i.e. because one object has too many electrons, and the other object has too few electrons), then the force between them will try and pull the electrons from the material with too many electrons towards the one with too few electrons, and if it succeeds in pulling these electrons across, then the from of these electrons becomes an electric current. If you are clever, you can use this flow of electrons to do useful work for you (e.g. drive an electric motor, or emit light), just as you can use a flow of water to drive a water wheel.
-
wow...THANK YOU SO MUCH. How come we can't teach this in high school, or college even(i had a basic physics class, didn't REALLY understand anything) hahaha. This is like basic knowledge. I mean, i know the knowledge source(mathematic definitions for the explanation) is alot more complex but your explain was great and easy to understand. YOU SHOULD WRITE A BOOK...seriously.
Thank so much for explaining that, that's all I really wanted to know, it frustrates me that it's so hard to get basic info like that. Look forward to future posts from me cause this site rocks.
-
Guys, can we get this right, please.
I know that, in ancient times they referred to voltage in terms of an 'electromotive force.
BUT electrical voltage - or POTENTIAL DIFFERENCE is a difference in ENERGY - not a force or a pressure. There is a huge difference between the concept of a force and the concept of an energy difference. If you want a cat's chance in hell of further understanding, start from the right place in elementary thinking.
The definition of the volt relates to electric charge and to energy transferred.
"When one coulomb of charge is raised to a potential of one volt, one joule of energy is transferred."
Or "a volt is one joule per coulomb", if you like.
SO energy transferred is volts times charge.
Also (more familiarly) power is volts times electric current.
I am surprised that people are saying this is not taught in school - it is taught to virtually every Science student at GCSE in the UK.
Of course, forces make charges move but the force ain't the voltage - the force is the volts per metre or the potential gradient!!!
Basic textbook stuff - textbooks are in all the shops if you need to find one.
-
Of course, forces make charges move but the force ain't the voltage - the force is the volts per metre or the potential gradient!!!
OK, I was aware of that even as I wrote - but I was just worried about overcomplicating what was already a long explanation over a lot of ground, and the notion of volts per metre becomes even more complex when one deals with materials of different resistance (simple enough when one is dealing with air - but mix two conductors of different resistance, and suddenly one gets a lot more complex explaining it all).
I felt that what I had explained was enough to explain how the voltage difference creates the force to move electrons, without getting into writing an entire book covering all the bits that I left out.
Strictly speaking, I suppose part of the problem is the inconsistent use of the word 'force'. I started by referring to the electric force being a force like the gravitational force; but ofcourse technically you can say neither qualify as a force by the definition you use, but are simply potential energy levels - but to a layman, they both represent forces of nature.
-
but to a layman, they both represent forces of nature.
That's fine if you just want to reinforce the idea of "ain't nature a wonderful mystery"
The problem with trying, actually, to explain things to laymen in solely laymen's terms is the risk of sustaining or amplifying mis-conceptions. This doesn't help. You, surely, have to introduce new ideas and a hint of rigour.
Here is a way of looking at it that should help the layman:
There are two roads down a hill. Both go from the top to the bottom.
One road has a gently slope (the long one) and the other one is steep.
Let's ignore friction and air resistance etc.
If you freewheel down on a bicycle on either road, you will end up at the SAME SPEED when you get to the bottom. i.e. you will have gained the same amount of kinetic energy because you will have lost the same amount of Gravitational Potential Energy (the mechanical equivalent to the Voltage or Potential Difference). It's easy to appreciate that the downhill force on the gentle slope is less than on the steep slope - but it acts over a longer distance. It depends on the 'gradient' of the road. The rate at which the bike gets kinetic (movement) energy is the rate at which it drops in height - or the rate it loses Potential Energy.
You could use this energy, if you liked, to heat up your brakes and even boil some water with the resulting heat. Same amount of heat available in both cases.
When electrons flow through through a wire / heater / light bulb/ motor they don't actually gather speed because the energy is being transferred as they flow through the device (as if they had the brakes on). The energy transferred goes into operating the device.
In electrical terms, you will have taken a charge through the same amount of Potential Difference, or 'voltage', however long the wire. If it's a 12V supply voltage, there's 12J of energy given to each coulomb of charge that flows.
The actual ' force' on your electric charges depends, not only on the voltage but on the distance the charges have to flow, or the 'gradient' (volts per metre), or the Electric field. The size or resistance of your device does not affect this - so you have, actually, simplified the explanation(?).
There is a circumstance in which electrons actually do pick up speed and that is when they are in a vacuum and when there is an electric field; say, between the electrodes in your TV tube. Under those conditions, they can reach very high speeds - a sizeable fraction fo the speed of light, even!