What flows inside wires? It has several names:
If we’d never learned the word “gallon”, and if we had no idea that water even existed, how could we hope to understand “flow?” We might decide that “current” was flowing through dry empty pipes. We might even decide that “current” was an abstract concept. Or we might decide that invisible wetnesswas moving along through the pipes. Or we could just give up on trying to understand plumbing at all. Instead we could concentrate on the math and do extremely well on any physics test, but we wouldn’t end up with any gut-level understanding. That’s the problem with electricity and amperes.
We only can understand the electrical flow in wires (the amperes) if we first understand the stuff that flows inside wires. What flows through wires? It’s the charge, it’s the metal’s own particle-sea, the Coulombs…
“Charge” is the stuff inside wires, but usually nobody tells us that all metals are always jam-packed full of movable charge. Always. A hunk of metal is like a tank full of water. Shake a metal block, and the “water” swirls around inside. This “water” is the movable electric charge found inside the metal. In our science classrooms we call this by the name “electron sea,” or even “electric fluid.” This movable charge is part of all metals. In copper, the electric fluid is actually the outer electrons of all the copper atoms. In any metal, the outer electrons do not orbit the individual atoms. The electrons do not behave as textbook diagrams usually depict atoms. Instead, the atoms’ outer electrons drift around inside the metal as a whole.
Note that this charge-stuff is “uncharged”, it is neutral. It’s uncharged charge! Is this even possible? Yes. On average, the charge inside a metal is neutralized because each movable electron has a corresponding proton within an atom nearby. Each electron is always fairly close to a proton. The electric force-fields from the two opposite charges cancel each other out. The overall charge is zero because equal quantities of opposite polarity are both present. For every positive there is a negative. But this doesn’t mean that the charge-stuff is gone. Even though the average amount of charge inside a metal is cancelled out, we can still cause one polarity of charge to move along while the other polarity remains still. For this reason, an electrical current is a flow of “uncharged” charges. Metal is made of negative electrons and positive protons; it’s like a positive sponge soaked with negative liquid. We can make this “negative liquid” flow along.
The faster the charge-stuff moves, the higher the amperage. Watch out though, since amperes are not just the speed of the charges. The MORE charge-stuff that flows, (flows through a bigger wire for example,) the higher the amperage. And a fast flow of charge through a narrow wire can have thesame amperes as a slow flow of charge through a bigger wire. Double the speed of charges in a wire and you double the current. Pinch a wire thinner, and the charges in the thin section flow faster. But if you keep the speed of a wire’s charges constant, then increase the size of the wire, you also increase the amperes.
Here’s a way to visualize it. Bend a metal rod to form a ring, then weld the ends together. Remember that all metals are full of “liquid” charge, so the metal ring acts like a water-filled loop of tubing. If you push a magnet’s pole into this ring, the magnetic forces will cause the electron-stuff within the whole ring to turn like a wheel (as if the ring contained a movable drive-belt). By moving the magnet in and out of the metal donut, we pump the donut’s movable charges, and the charges flow in a circle. That’s essentially how electric generators work.
Electric generators are magnet-driven charge pumps. The changing magnetic field pushes the wire’s movable sea of charges, creating the amperes of charge flow, but this can only occur when a closed ring or “complete circuit” exists. Break the ring and you create a blockage, since the charges can’t easily escape the metal to jump across the break in the ring. If the charges within the metal are like a drive-belt, then a gap in the ring is like a “brake” that grabs the belt in one spot and stops all belt motion. A complete metal ring is a “closed electric circuit,” while a broken ring is an “open circuit.”
A battery is another kind of charge pump. Cut a slot in our metal ring and install a battery in the slot. This lets the battery pump the ring’s charge-stuff in a circle. Batteries and generators are similar in that both can pump charge through themselves and back out again. With a battery installed in our metal ring, the battery draws charge into one end and forces it out the other, and this makes the entire contents of the metal ring start moving. Make another cut in the metal ring, install a light bulb in the cut, and then the “friction” of the narrow light bulb filament against the flowing charge-stuff creates high temperatures, and the wire filament inside the bulb glows white-hot. The battery drives the ring of charge into motion, the charge moves along like a solid rubber drive belt, and the light bulb “rubs” against the moving charge, which makes the filament grow hot.
Important note: inside wires, usually the charge-stuff flows extremely slowly; slower than centimeters per minute. Amperes are an extremely slow, circular flow. See SPEED OF ELECTRICITY for info.
What is power? The word “power” means “energy flow.” In order to understand these ideas, it might help if you avoid using the word “power” at the start. The word “power” means “energy flow”, so instead you can practice thinking in terms of energy-flow instead of in terms of the word “power.” Also think in terms of joules-per-second rather than watts, and eventually you’ll gain a good understanding of the ideas behind them. Then, once you know what you’re talking about, you can start speaking in shorthand. To use the shorthand, don’t say “energy flow”, say “power.” And say “watts” instead of “joules per second.” But if you start out by saying “power” and “watts”, you might never really learn what these things are, because you never really learned about the energy flow and the joules.
FLOWING ELECTRICAL ENERGY
How is electric current different than energy flow? Let’s take our copper ring again, the one with the battery and the light bulb. The battery speeds up the ring of charge and makes it flow, while the light bulb keeps it from speeding up too much. The battery also injects joules of electrical energy into the ring, and the light bulb takes them out again. Joules of energy flow continuously between the battery and the bulb. The joules flow almost instantly: at nearly the speed of light, and if we stretch our ring until it’s thousands of miles long, the light bulb will still turn off immediately when the battery is removed. (Well, not really immediately. There will still be some joules left briefly racing along the wires, so the bulb will stay lit for a tiny instant , until all the energy arrives at the bulb.) Remove the battery, and the light bulb goes dark ALMOST instantly.
AMPERES are NOT a FLOW of ENERGY
But what are Joules? That’s where the electromagnetism comes in. When joules of energy are flying between the battery and the bulb, they are made of invisible fields. The energy is partly made up of magnetic fields surrounding the wires. It is also made from the electric fields which extend between the two wires. Electrical-magnetic. Electromagnetic fields. The joules of electrical energy are the same “stuff” as radio waves. But in this case they’re attached to the wires, and they flow along the columns of movable electrons inside the wires. The joules of electrical energy are a bit like sound waves which can flow along an air hose. Yet at the same time, electrical energy is very different than sound waves. The electrical energy flows in the space around the wires, while the electric chargeflows inside the wires.
Remember the battery in the copper ring from above? The battery acted as a charge pump. It pulled charge-stuff out of one side of the ring, and pushed it into the other side. Not only did this force the circle of charges to begin moving, it also caused a voltage-difference to appear between the two sides of the ring. It also caused an electrostatic field to appear in the space surrounding the ring. The charges within the copper ring began moving because they responded to the forces created by the voltage surrounding the ring. In this way the voltage is like pressure. By pushing the charges from one wire to the other, a voltage causes the two wires to become positive and negative… and the positive and negative wires produce a voltage. (In hydraulics we would use a pressure to drive water into a pipe, and because we drove water into a pipe the pressure in that pipe would rise.)
So, the battery “charged up” the two halves of the copper ring. The light bulb provided a path to discharge them again, and this created the flow of charge in the light bulb filament. The battery pushes charge through itself, and this also forces a pressure-imbalance in the ring, and forces charges to flow through the light bulb filament. But where does energy fit into this? To understand that, we also have to know about electrical friction or “resistance.” Also: What is Voltage?
Whew. NOW we can get back to energy flow.
VOLTS, AMPS, OHMS, ENERGY FLOW
Here’s the simplest electrical relation: THE HARDER THE PUSH, THE FASTER THE FLOW. “Ohm’s Law”, can be written like this:
VOLTS/OHMS = COULOMBS/SEC The harder the push, the faster flows the charge
VOLTS/OHMS = AMPERES Voltage across resistance causes current
Ohm’s law has another feature: THE MORE FRICTION YOU HAVE, THE SLOWER THE FLOW. If you keep the voltage the same (in other words, you keep using the same battery to power your light bulb), and if you double the resistance, then the charges flow slower, and you get half as much current. Increasing the resistance is easy: just hook more than one light bulb in a series chain. The more light bulbs, the more friction, which means that current is less and each bulb glows more dimly. In the bicycle wheel analogy mentioned above, a chain of light bulbs is like several thumbs all rubbing on the same spinning tire. The more thumbs, the slower the tire moves.
Here’s a third way of looking at Ohm’s law: WHEN A CONSTANT CURRENT ENCOUNTERS FRICTION, A VOLTAGE APPEARS. We can rewrite Ohm’s law to show this:
AMPERES x OHMS = VOLTS A flow of charge produces a voltage if it encounters resistance
But what about joules and watts? Whenever a certain amount of charge is pushed through an electrical resistance, some electrical energy is lost from the circuit and heat is created. A certain amount of energy flows into the “frictional” resistor every second, and a certain amount of heat energy flows back out again. If we increase the voltage, then for the same hunk of charge being pushed through, more energy flows into the resistor and gets converted to heat. If we increase the hunk of charge, same thing: more heat flows out per second. Here’s how to write this:
VOLTS x COULOMBS = JOULES It takes energy to push some charge against the voltage pressure
The above equation isn’t used very often. Instead, we usually think in terms of charge flow and energy flow, not in terms of hunks of charge or hunks of energy which move. However, thinking in terms of charge hunks or energy hunks makes the concepts sensible. Once you grasp the “hunks” concepts, once you know that energy is needed to push each hunk of charge against a voltage force, afterwards we can rewrite things in terms of amps and watts. Afterwards we can say that it takes a FLOW of energy (in watts) to push a FLOW of charge (in amps) against a voltage. Yet first it’s important to understand the stuff that flows. Think in terms of coulombs of charge and joules of energy.
The charge-flow and the energy-flow are usually written as amps and watts. This conceals the fact that some quantities of “stuff” are flowing. But once we understand what’s really going on inside a circuit, it’s simpler to write amperes of charge-flow and watts of energy-flow:
VOLTS x COULOMBS/SEC = JOULES/SEC It takes a flow of energy to make charge flow forward against pressure
VOLTS x AMPERES = WATTS Pushing a current through a voltage requires energy flow or "power."
VOLTS x (VOLTS/OHMS) = WATTS Voltage applied across ohms uses up a constant flow of electrical energy
Here’s one final equation. It’s almost the same as the one above, but voltage is hidden rather than ampereage:
(AMPERESxOHMS) x AMPERES = WATTS When charge is flowing against ohms, electrical energy is being used up
And finally, here are a couple of things which can mess you up. Think about flowing power. Try to visualize it. I hope you fail! Remember… POWER DOESN’T FLOW! The word “power” means “flow of energy.” It’s OK to imagine that invisible hunks of electrical energy are flowing across a circuit. That’s sensible. Electrical energy is like a stuff; it can flow along, but “energy flow” cannot flow. Power is just flowing energy, so “power” itself never flows. Beware, sincemany people (and even textbooks) will talk about “flows of power.” They are wrong. They should be talking about flows of electrical energy. “Flow of power” is a wrong (and fundamentally stupid) concept.
Guess what. The same books and people who talk about “flows of power” will also talk about “flows of current.” They’ll try to convince you that “current” is a stuff that can flow through wires. Ignore them, they’re wrong. Elecric charge is like a stuff that exists inside all wires, but current is different. When pumped by a battery or a generator, the wire’s internal charge-stuff starts flowing. We call the flow by the name “an electrical current.” But there is no such STUFF as “current.” Current cannot flow. (Ask yourself what flows in rivers, current… or water? Can you go down to the creek and collect a bucket of “current?”) If you want a big shock, read through a textbook or an electronics magazine and see how many times the phrase “current flow” appears. Like the phrase “power-flow,” it’s not just wrong, it’s STUPID.
Authors are trying to teach us about flows of charge, but instead they end up convincing us that “current” is a kind of stuff! It’s so weird. And it’s a bit frightening because it’s so widespread. It’s very rare to find a book which avoids the phrase “current flow” and explain charge-flow. Most books instead talk about this crazy flow of “current.” It’s no wonder that students have trouble understanding electricity. They essentially think that waterpipes are totally different from circuits because you can fill a glass with water, but who on earth can imagine filling a container with “current?”
OK, I’ve run out of steam for now. Ooo! Ooo! No I haven’t. I must now go on a crusade about How Capacitors Are Explained Wrong. Then I’ll go on and on about Why most explanations of transistors basically suck.
From Amasci @ http://amasci.com/elect/vwatt1.html
For more info about electromagnetism seehttp://nexusilluminati.blogspot.com/search/label/electromagnetism
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