Because the answer to this Electricity question is a pretty long (yet interesting!!) one, we’ll be sharing part of the article here. For the rest of this amazingly intuitive article, please click here.
Here’s the extremely short answer…
Conductive objects are always full of movable electric charges, and the overall motion of these charges is called an ‘electric current.’ Voltage can cause electric currents because a difference in voltage acts like a difference in pressure which pushes the conductors’ own charges along. A conductor offers a certain amount of electrical resistance or “friction,” and the friction against the flowing charges heats up the resistive object. The flow-rate of the moving charges is measured in Amperes. The transfer of electrical energy (as well as the rate of heat output) is measured in Watts. The electrical resistance is measured in Ohms. Amperes, Volts, Watts, and Ohms.
Not so simple? Then let’s take a much deeper look. First the watts and amperes. Watts and amps are somewhat confusing because both are flow-rates, yet we rarely talk about the “stuff” which does the flowing. I suspect it’s impossible to understand a flow rate without first understanding the substance which flows. Take water flow for example. Could we really understand gallons-per-second, if we didn’t understand gallons? And if we’d never touched water? It’s not easy to understand flow rates like Amperes or Watts without understanding the “flowing material.” OK, first let’s do the Amperes.
Since a current is a flow of charge, the common expression “flow of current” should be avoided, since literally it means “flow of flow of charge.”
-MODERN COLLEGE PHYSICS. Sears,Zemanski,Richards,Wher
Current isn’t a stuff. Electric currents are the flows of a stuff. OK then, what’s the name of the stuff that flows during an electric current? The flowing stuff is called “Charge.”
A quantity of charge is measured in units called COULOMBS, and the word Ampere means the same thing as “one Coulomb of charge flowing per second.” If we were talking about water, then Coulombs would be like gallons, and amperage would be like gallons-per-second.
What flows inside wires? It has several names:
- Charges of electricity
- Charged atoms (ions in salt water etc.)
- Electric charge
- Electrical substance
- The Electron sea
- Ion population
- The ocean of charge
- Electric fluid
Why are Amperes confusing? Simple: textbooks almost always teach us about amperes and current, but without first clearly explaining the coulombs and charges! Suppose that we had no name for “water,” and yet our teachers wanted us to learn all about the mysterious flow inside metal plumbing pipes? Suppose we were required to understand “gallons-per-second,” but we had to do this without knowing anything about water, or about gallons?
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 wetness was 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, memorize equations. 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 fact it’s part of all conductors, from plasma to battery acid to charged dust storms. In copper metal, 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 4th grade textbook diagrams usually depict atoms. Instead, the atoms’ outer electrons drift around inside the metal as a whole.
The movable charge-stuff within a metal gives the metal its silvery metallic color. We could even say that charge-stuff is like a silver liquid. At least it appears silver-colored when it’s in metals. When it’s within some other materials, the movable charges don’t usually look silvery. “Silvery-looking charges” applies to metals, but isn’t a hard and fast rule.
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. Copper is made up of free electrons and positive copper ions. 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.
Whenever the charge-stuff within metals is forced to flow, we say that “electric currents” are created. The word “current” simply means “charge flow.” We normally measure the flowing charges in terms of amperes.
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 the same 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, yet the current stays the same. But if you keep the speed of a wire’s charges constant, and 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.
Watts have the same trouble as Amperes. “Watts” are the name of an electrical flow… but what stuff does the flowing? Energy! A “watt” is just a fancy way of saying “quantity of electrical energy flowing per second.” But what is a quantity of electrical energy? I’ll get to that in a sec. But briefly, any sort of energy is measured in terms of Joules. A joule of electrical energy can move from place to place along the wires. When you transport one joule of energy through a channel every second, the flow-rate of energy is 1 Joule/Sec, and “one Joule per second” means “one watt.” (It might help keep things traight if you erase all the “watts” in your textbook, and instead write “joules per second.)
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
OK, what then is electrical energy? It has another name: electromagnetism. Electrical energy is the same stuff as radio waves and light. It’s made up of magnetic fields and electrostatic fields. A joule’s worth of of radio waves is the same as a joule of electrical energy. But what does this have to do with understanding electric circuits? Quite a bit! I’ll delve deeper into this. But first…
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.
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