"Static electricity" exists whenever there are unequal amounts of positive and negative charged particles present. It doesn't matter whether the region of imbalance is flowing or whether it is still. Only the imbalance is important, not the "staticness." To say otherwise can cause several sorts of confusion.
All solid objects contain vast quantities of positive and negative particles whether the objects are electrified or not. When these quantities are not exactly equal and there is a tiny bit more positive than negative (or vice versa), we say that the object is "electrified" or "charged," and that "static electricity" exists. When the quantities are equal, we say the object is "neutral" or "uncharged." "Charged" and "uncharged" depends on the sum of opposite quantities. Since "static electricity" is actually an imbalance in the quantities of positive and negative, it is wrong to believe that the phenomenon has anything to do with lack of motion, with being "static." In fact, "static electricity" can easily be made to *move* along conductive surfaces. When this happens, it continues to display all it's expected characteristics as it flows, so it does not stop being "static electricity" while it moves along very non-statically! In a high voltage electric circuit, the wires can attract lint, raise hair, etc., even though there is a large current in the wires and all the charges are flowing (and none of the electricity is "static.") And last, when any electric circuit is broken and the charges stop flowing, they do *not* turn into "static electricity" and begin attracting lint, etc. A disconnected wire contains charges which are not moving (they are static,) yet it contains no "static electricity!"
To sort out this craziness, simply remember that "static electricity" is not a quantity of unmoving charged particles, and "static electricity" has nothing to do with unmoving-ness. If you believe that "static" and "current" are opposite types of "electricity," you will forever be hopelessly confused about electricity in general.
Monday, November 16, 2009
ELECTRIC POWER FLOWS FROM GENERATOR TO CONSUMER?
Electric power cannot be made to flow. Power is defined as "flow of energy." Saying that power "flows" is silly. It's as silly as saying that the stuff in a moving river is named "current" rather than named "water." Water is real, water can flow, flows of water are called currents, but we should never make the mistake of believing that water's motion is a type of substance. Talking of "current" which "flows" confuses everyone. The issue with energy is similar. Electrical energy is real, it is sort of like a stuff, and it can flow along. When electric energy flows, the flow is called "electric power." But electric power has no existence of its own. Electric power is the flow rate of another thing; electric power is an energy current. Energy flows, but power never does, just as water flows but "water current" never does.
The above issue affects the concepts behind the units of electrical measurement. Energy can be measured in Joules or Ergs. The rate of flow of energy is called Joules per second. For convenience, we give the name "power" to this Joule/sec rate of flow, and we measure it in terms of Watts. This makes for convenient calculations. Yet Watts have no physical, substance-like existence. The Joule is the fundamental unit, and the Watt is a unit of convenience which means "joule per second."
I believe that it is a good idea to teach only the term "Joule" in early grades, to entirely avoid the "watt" concept. Call power by the proper name "joules per second". Only introduce "watts" years later, when the students feel a need for a convenient way to state the "joules per second" concept. Unfortunately many textbooks do the reverse, they keep the seemingly-complex "Joule" away from the kids, while spreading the "watt" concept far and wide! Later they try to explain that joules are simply watt-seconds! (That's watts TIMES seconds, not watts per second.)
If you aren't quite sure that you understand watt-seconds, stop thinking backwards and think like this: Joules are real, a flow of Joules is measured in Joules per second, and "Watts" should not interfere with these basic ideas.
The above issue affects the concepts behind the units of electrical measurement. Energy can be measured in Joules or Ergs. The rate of flow of energy is called Joules per second. For convenience, we give the name "power" to this Joule/sec rate of flow, and we measure it in terms of Watts. This makes for convenient calculations. Yet Watts have no physical, substance-like existence. The Joule is the fundamental unit, and the Watt is a unit of convenience which means "joule per second."
I believe that it is a good idea to teach only the term "Joule" in early grades, to entirely avoid the "watt" concept. Call power by the proper name "joules per second". Only introduce "watts" years later, when the students feel a need for a convenient way to state the "joules per second" concept. Unfortunately many textbooks do the reverse, they keep the seemingly-complex "Joule" away from the kids, while spreading the "watt" concept far and wide! Later they try to explain that joules are simply watt-seconds! (That's watts TIMES seconds, not watts per second.)
If you aren't quite sure that you understand watt-seconds, stop thinking backwards and think like this: Joules are real, a flow of Joules is measured in Joules per second, and "Watts" should not interfere with these basic ideas.
ELECTROMAGNET COILS USE UP ENERGY TO MAKE MAGNETISM?
Sustaining a magnetic field requires no energy. Coils only require energy to initially create a magnetic field. They also require energy to defeat electrical friction (resistance); to keep the charges from slowing down as they flow in wires. But if the resistance is removed, the magnetic field can exist continuously without any energy input. If electrically frictionless superconductive wire is used, a coil can be momentarily connected to an energy supply to create the field. Afterwards the power supply can be removed and both the current and the magnetic field will continue forever without further energy input.
ELECTRIC CHARGES ARE INVISIBLE?
Electric charges are easily visible to human eyes, even though their motion is not. "Electricity" is not invisible! Never has been. When you look at a metal wire, you can see the charges of electricity which would flow during electric currents. They are silvery/metallic in color. They give metals their mirrorlike shine. Some metals have other colors as well, brass and copper for instance. Yet in all cases, the "metallic"-looking stuff is the metal's electrons. A dense crowd of electrons looks silvery; "electric fluid" is a silver liquid. And if metals weren't full of movable electrons, they wouldn't look metallic.
During electric currents in metals, the atoms stay still, but the silvery electron-stuff flows slowly along. Unfortunately the human eye cannot see the electric flow. That's part of the reason that "electricity" is so mysterious. Think about it... in an aquarium full of water, you cannot see any water flowing unless there are bubbles or dirt being carried along. And whenever clean water is flowing through a transparent hose, you can't see any flow. Even if the water is flowing very fast, the water-filled hose just looks like an unmoving glass rod. Same with wires: there's no bubbles or dirt being carried along by the electric current, therefore you can't see anything moving. You can see the STUFF that flows, just as you can see the water in an aquarium, but you can't see any flowing stuff.
Even if human eyes could see single electrons, we still couldn't see an electrical flow since the current is extremely slow. Electrons in metals typically flow at a few centimeters per hour, even during high currents. That's slower than the minute hand on a clock! Electric currents OOZE along like silly-putty flowing across a tilted board.
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Seeing imbalances in charge
Here's a separate topic... while the metallic-looking sea of charges in a metal is easily seen, IMBALANCES of charge are not. This get's confusing, since many books call imbalances of charge by the name "charge." They will tell you that charge is invisible, yet they really mean that charge-imbalances are invisible.
Wires contain enormous amounts of movable negative charge in the form of electrons, but they also contain positive charge in the form of protons within the metal atoms. If the number of protons and electrons are equal, don't they cancel out? Doesn't that mean that no charge exists? No. It means that no IMBALANCE of charge exists.
An "uncharged" wire is still full of charge, it still contains positive and negative charge in huge but equal quantities. The word "uncharged" doesn't mean "without charge," instead it means "without charge-imbalance." Yet even if there are more electrons than protons, or fewer electrons than protons, this imbalance is invisible. It's invisible because the greatest difference attainable is incredibly tiny when compared to the amount of charge that's already there. If an object is highly charged; even charged up to millions of volts, the extra charge is like a teacup poured into an ocean. The difference is far too small to be seen.
During electric currents in metals, the atoms stay still, but the silvery electron-stuff flows slowly along. Unfortunately the human eye cannot see the electric flow. That's part of the reason that "electricity" is so mysterious. Think about it... in an aquarium full of water, you cannot see any water flowing unless there are bubbles or dirt being carried along. And whenever clean water is flowing through a transparent hose, you can't see any flow. Even if the water is flowing very fast, the water-filled hose just looks like an unmoving glass rod. Same with wires: there's no bubbles or dirt being carried along by the electric current, therefore you can't see anything moving. You can see the STUFF that flows, just as you can see the water in an aquarium, but you can't see any flowing stuff.
Even if human eyes could see single electrons, we still couldn't see an electrical flow since the current is extremely slow. Electrons in metals typically flow at a few centimeters per hour, even during high currents. That's slower than the minute hand on a clock! Electric currents OOZE along like silly-putty flowing across a tilted board.
------
Seeing imbalances in charge
Here's a separate topic... while the metallic-looking sea of charges in a metal is easily seen, IMBALANCES of charge are not. This get's confusing, since many books call imbalances of charge by the name "charge." They will tell you that charge is invisible, yet they really mean that charge-imbalances are invisible.
Wires contain enormous amounts of movable negative charge in the form of electrons, but they also contain positive charge in the form of protons within the metal atoms. If the number of protons and electrons are equal, don't they cancel out? Doesn't that mean that no charge exists? No. It means that no IMBALANCE of charge exists.
An "uncharged" wire is still full of charge, it still contains positive and negative charge in huge but equal quantities. The word "uncharged" doesn't mean "without charge," instead it means "without charge-imbalance." Yet even if there are more electrons than protons, or fewer electrons than protons, this imbalance is invisible. It's invisible because the greatest difference attainable is incredibly tiny when compared to the amount of charge that's already there. If an object is highly charged; even charged up to millions of volts, the extra charge is like a teacup poured into an ocean. The difference is far too small to be seen.
A "CONDUCTOR" IS A MATERIAL WHICH ALLOWS CHARGE TO PASS THROUGH IT?
The scientist's definition of the word "conductor" is different than the one above, and the one above has problems. For example, a vacuum offers no barrier to flows of electric charges, yet vacuum is an insulator. Vacuum is NOTHING, so how can it act as a barrier to electric current? Also, there is a similar problem with air: electric charges placed into the air can easily move along, yet air is an insulator. Or look at salt water versus oil. Oil is an insulator, while salt water is a conductor, yet neither liquid is able to halt the flow of any charges which are placed into it. How can we straighten out this paradox? Easy: use the proper definition of the word "conductor."
WRONG DEFINITION:
Conductor - a material which allows charges to pass through itself
BETTER:
Conductor - a material which can support an electric current
BEST:
Conductor - a material which contains movable electric charges
Here's an analogy:
Conductor - like a pipe which is already full of water
Insulator - like a pipe with frozen liquid; a pipe plugged by ice
If we place a Potential Difference across either air or a vacuum, no electric current appears. This is sensible, since there are few movable charges in air or vacuum, so there can be no electric current. If we place a voltage across a piece of metal or across a puddle of salt water, charges will flow and an electric current will appear, since these substances are always full of movable charges, and therefore the "voltage pressure" causes the charges to flow. In metal, the outer electrons of the atoms are not bound upon individual atoms but instead can move through the material, and a voltage can drive these "liquid" electrons along. But if we stick our wires into oil, there will be no electric current, since oil does not contain movable charges.
If we were to inject charges into a vacuum, then we WOULD have electric current in a vacuum. This is how TV picture tubes and vacuum tubes work; electrons are forcibly injected into the empty space by a hot filament. However, think about it for a second: it's no longer a vacuum when it contains a cloud of electrons! Maybe we should change their name to "electron-cloud tubes" rather than "vacuum tubes", since the electron cloud is required before there can be any conductivity in the space between the plates. (But vacuum tubes already have another name, so this would just confuse things. They are called "hollow-state devices." As opposed to "solid state devices?" Nyuk nyuk.)
WRONG DEFINITION:
Conductor - a material which allows charges to pass through itself
BETTER:
Conductor - a material which can support an electric current
BEST:
Conductor - a material which contains movable electric charges
Here's an analogy:
Conductor - like a pipe which is already full of water
Insulator - like a pipe with frozen liquid; a pipe plugged by ice
If we place a Potential Difference across either air or a vacuum, no electric current appears. This is sensible, since there are few movable charges in air or vacuum, so there can be no electric current. If we place a voltage across a piece of metal or across a puddle of salt water, charges will flow and an electric current will appear, since these substances are always full of movable charges, and therefore the "voltage pressure" causes the charges to flow. In metal, the outer electrons of the atoms are not bound upon individual atoms but instead can move through the material, and a voltage can drive these "liquid" electrons along. But if we stick our wires into oil, there will be no electric current, since oil does not contain movable charges.
If we were to inject charges into a vacuum, then we WOULD have electric current in a vacuum. This is how TV picture tubes and vacuum tubes work; electrons are forcibly injected into the empty space by a hot filament. However, think about it for a second: it's no longer a vacuum when it contains a cloud of electrons!
LIGHTNING RODS DISCHARGE THE CLOUDS?
Make a model "landscape", install some lightning rods on the tiny houses, then bring a "storm cloud" nearby: bring the metal sphere of a VandeGraaff Electrostatic generator over your small town. The strong electric charge on the sphere will vanish. Doesn't this prove that lightning rods can discharge a thunderstorm? Nope.
The above demonstration was thought at one time to be accurate, and this old mistake is still in many books. In reality, lightning rods cannot remove the charge-imbalance from a thunderstorm. The scale of the typical demo is wrong. The stormcloud is a few miles up, and a few miles across, yet the lightning rod on the house is only a few feet tall. Therefore the metal-sphere "cloud" should be fairly large, and "Rod" should be far less than 1mm tall and attached to a wide metal ground plate.
The typical demonstration doesn't illustrate a lightning rod, it illustrates a 2000-ft radio tower or extremely tall office building.
Think about it: how can a tiny needle affect cubic kilometers of strong e-field? How could the relatively tiny current from a metal rod discharge a cloud that's over 1KM away. It can't! To do so, it would have to emit a hurricane wind made of ionized air. Unfortunately the lightning rod on your roof only emits about the same current as the needle in the model town: it emits a few microamperes. In other words, the scale model is not correct because the current coming from the needle is way too high. In order to be at the proper scale, the current would have to be hundreds of thousands of times smaller; too small to affect the VDG machine's charge.
HUMID AIR IS CONDUCTIVE?
Electrostatic experiments don't work very well under humid conditions. Some books state that the water vapor in the air makes the air conductive. Wrong. In reality the problem is caused by the liquid water that becomes adsorbed on surfaces of objects.
In order to make the air conductive, we'd have to fill it with movable charged particles. Evaporated water is not made of charged particles (ions,) instead it's made of neutral molecules, so the high humidity does not significantly affect the conductivity of the air. Even suspended water droplets (fog) does not significantly affect conductivity. For fog to be conductive, the individual droplets would have to posess an electric charge.
However, during humid conditions most insulators develop a surface layer of conductive water mixed with contaminants (including dissolved salts which makes this layer of water conductive.) If you find that you can't separate any charges by rubbing a balloon on your head, it's because the humid air has made the balloon and the hair very slightly damp. The air remains nonconductive, but surfaces of insulators become conductive when damp. Conductive surfaces don't separate any opposite charges when rubbed together. Cure this by warming them (drying them) with a blow-dryer. If a pair of insulators is sufficiently dry, it will "generate charge" even under very humid conditions. If conductive air were the culprit, this cure couldn't work
In order to make the air conductive, we'd have to fill it with movable charged particles. Evaporated water is not made of charged particles (ions,) instead it's made of neutral molecules, so the high humidity does not significantly affect the conductivity of the air. Even suspended water droplets (fog) does not significantly affect conductivity. For fog to be conductive, the individual droplets would have to posess an electric charge.
However, during humid conditions most insulators develop a surface layer of conductive water mixed with contaminants (including dissolved salts which makes this layer of water conductive.) If you find that you can't separate any charges by rubbing a balloon on your head, it's because the humid air has made the balloon and the hair very slightly damp. The air remains nonconductive, but surfaces of insulators become conductive when damp. Conductive surfaces don't separate any opposite charges when rubbed together. Cure this by warming them (drying them) with a blow-dryer. If a pair of insulators is sufficiently dry, it will "generate charge" even under very humid conditions. If conductive air were the culprit, this cure couldn't work
"ELECTRICITY IS WEIGHTLESS?
MORE TRUE STATEMENTS ABOUT "ELECTRICITY"
- In a DC circuit, the electricity within the wires flows exceedingly slowly; at speeds around inches per minute. At the same time, the electrical energy flows at nearly the speed of light.
- If we know the precise amount of electricity flowing per second through a wire (the Amperes,) this tells us nothing about the amount of energy being delivered per second into a light bulb (the Watts.) Amperes are not Watts, an electric current is not a flow of energy; they are two different things.
- In an electric circuit, the flow of the electricity is measured in Coulombs per second (Amperes.) The flow of energy is measured in Joules per second (Watts.) A Coulomb is not a Joule, and there is no way to convert from Coulombs of charge into Joules of energy, or from Amperes to Watts. A quantity of electricity is not a quantity of energy.
- Electrical energy is electromagnetism; it is composed of an electromagnetic field. On the other hand, the particles of electricity (electrons) flowing within a wire have little resemblance to an electromagnetic field. They are matter. Electricity is not energy, instead it is a major component of everyday matter.
- In an electric circuit containing coils, if we reverse the polarity of voltage while the direction of the flowing electricity remains the same, then the direction of the flowing energy will be reversed. Current same; energy flow reversed? Yes. A flow of energy does not follow the direction of the flowing electricity. You can know everything about the direction of the electricity within a wire, but this tells you nothing about the direction of the flowing electrical energy.
- In any electric circuit, the smallest particle of electrical energy is NOT the electron. The smallest particle of energy is the "unit quantum" of electromagnetic energy: it is the photon. Electrons are not particles of EM energy, neither do they carry the energy as they travel in the circuit. Electricity is 'made' of electrons and protons, while electrical energy is electromagnetism and is 'made' of photons.
- In the electric power grid, a certain amount of energy is lost because it flys off into space. This is well understood: electrical energy is electromagnetic waves travelling in the air, and unless the power lines are twisted or somehow shielded, they will act as 60Hz antennas. Waves of 60Hz electrical energy can spread outwards into space rather than following the wires. The power lines can even receive extra 60Hz energy from space, from magnetic storms in Earth's magnetosphere. Electric energy is gained and lost to empty space while the charges of electricity just sit inside the wires and wiggle. Energy is not electricity.
- In an electric circuit, electrical energy does not flow inside the copper. Instead it flows in the empty air surrounding the wires. This fact is hidden because we calculate energy flow by multiplying voltage times current. College-level physics books describe a less misleading method of measuring this energy flow: take the vector cross-product of the E and M components of the electromagnetic field at all points in a plane penetrated by the wires. We call this the Poynting Vector field. Add these measurements together, and this tells us the total energy flow (the Joules of energy that flow each second through the plane.) In other words, in order to discover the rate of energy flow, don't look at the flowing electrons. The electricity flow tells us little. Instead look at the electromagnetic fields which surround the wires.
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