Up to SCIENCE HOBBYIST | Up to MISCONCEPTIONS

"ELECTRICITY" MISCONCEPTIONS IN K-6 TEXTBOOKS - - -William J. Beaty


"ELECTRICITY" IS A PHENOMENON COMPOSED OF ENERGY? Wrong.

Actually, "Electricity" does not exist. The term "electricity" is a catch-all word with many meanings. Unfortunately these meanings are contradictory, and this leads to the unsettling fact that there is no single substance or energy called "electricity." When we say "quantity of electricity," we could be talking about quantities of charged particles. But we could also be talking about quantity of energy, quantity of current, or potential, forces, fields, net charge, power, or even about electrical phenomena. All of these are found as separate dictionary definitions of the word "electricity." But current is not power, particles are not fields, and charge is not energy. "Quantity of Electricity" is a meaningless concept because of the contradictory definitions of the word "electricity."

Much of this problem would vanish if we used the word "electricity" only to refer to a field of science or class of phenomena. This is the way we use the words "physics" or "optics." Then, if we needed to get down to details, we would never say "electricity." Instead we would use words like "charges," "energy", "current," etc. We do use the word "electricity" this way occasionally. But then we immediately turn around and do the equivalent of teaching our children that optics is a substance, or that physics is a kind of energy. "Optics" is a substance which comes out of the light bulb and passes through the lens, right? And when you ride a bicycle, "physics" comes out of your muscles and makes the wheels turn?

Below are a few examples of errors caused by the contradictory meanings.


THE "ELECTRICITY" WHICH FLOWS IN WIRES IS SUPPLIED BY BATTERIES OR GENERATORS? Wrong.

Electric currents in copper wires are a flow of electrons, but these electrons are not supplied by batteries. They come from the copper atoms in the wire. The electrons were in the circuit before the battery was connected. They were even there before the copper was mined and made into wires! Batteries and generators do not create these electrons, they merely pump them, and the electrons are like a pre-existing fluid that is always found within all wires. In order to understand electric circuits, we imagine that all the wires are pre-filled with a sort of "liquid electricity."

To clarify this, ask yourself exactly where the "electricity" comes from when a generator powers a light bulb. A generator takes electrons in from one terminal and simultaneously spits them out the other one. At the same time, the generator pushes electrons through the coil of wire inside itself and through the rest of the circuit. Where is the source of "electricity?" When we include the generator in the circuit, we find that the circuit is a continuous closed loop of wire, and we can find no original source of the "electricity." A generator or battery is like a closed-loop pump, but it does not supply the substance being pumped. But we were all taught that "batteries and generators create current electricity." This phrase forms a serious conceptual stumbling block (at least it did for me!) To fix it, change the statement to read like this instead: "batteries and generators cause electric charge to flow."

A battery or generator is like your heart: it moves blood, but it does not create blood. When a generator stops, or when the metal circuit is opened, all the electrons stop where they are, and the wires remain filled with electric charges. But this isn't unexpected, because the wires were full of vast quantities of charge in the first place.


ELECTRONS IN WIRES JUMP FROM ATOM TO ATOM DURING A CURRENT? Wrong.

When separate atoms of copper are brought together to form a bulk metal material, something unexpected happens. The outer electron of each copper atom leaves. The outer electrons all begin "orbiting" around and among ALL the atoms in the metal. In a sense, the metal's electrons are "jumping" from atom to atom all the time, even when there is no electric current applied. As a result, a metal acts like a solid sponge which has been soaked with "liquid charge." That's what makes wires so wonderful: they act like pre-filled pipes. The orbiting motion of the metal's electrons is similar to the thermal vibrations of a gas. For this reason we normally ignore this motion, just as we ignore the vibration of air molecules when we talk about "wind." Electrons in metals are not stuck to individual atoms, so electrons do not need to "jump" during an electric current.

THE "ELECTRICITY" INSIDE OF WIRES MOVES AT THE SPEED OF LIGHT ? Wrong.

In metals, electric current is a flow of electrons. Many books claim that these electrons flow at the speed of light. This is incorrect. Electrons actually flow quite slowly, at speeds on the order of centimeters per minute. It's the energy in the circuit which flows fast, not the electrons. When the electrons at one point in the circuit are pumped, electrons in the entire loop of the circuit are forced to flow, and energy spreads almost instantly throughout the entire circuit. This happens even though the electrons move very slowly. Imagine a large wheel. If you give it a spin, the entire wheel moves as a unit, and this is how you transmit mechanical energy almost instantly to all parts of the wheel's rim. But the wheel itself didn't move very fast. The material of the wheel is like the electrons in a wire. Electrical energy is like the "jerk," the mechanical energy wave which you sent to all parts of the wheel when you gave it a spin. Mechanical energy moves incredibly quickly to all parts of the wheel, but the wheel's atoms didn't have to rapidly travel anywhere in order for this to happen. MORE


THE ELECTRIC ENERGY IN A CIRCUIT FLOWS IN A CIRCLE? Wrong.

When you connect a light bulb to a battery, energy moves from the battery to the bulb. This is a one-way flow. If this phenomena is examined in great detail, we find that electrical energy is composed of electromagnetic fields. We find that it moves as wave energy, that it exists only outside of the wires, and most importantly, that it TRAVELS ONE WAY along BOTH wires on its trip from the battery to the bulb. The energy did not travel in a circle. So, when you plug a lamp into a wall socket, you should not imagine that the AC energy is a mysterious invisible entity traveling back and forth inside the wires. Instead you should think of it as a mysterious invisible flow that comes out of the outlet, runs along the outside of BOTH wires, then dives into the filament of the light bulb.


ELECT. LEAVES ONE BATTERY PLATE, THEN RETURNS TO THE OTHER? Not quite.

The real path of electric current is THROUGH the battery. Some books imply (or even state outright) that when a battery is connected in a complete circuit, the charges flow only in the wires and within the battery's plates, and no charges flow in the chemicals between those plates. This is wrong. In any electric circuit, the path of the electric current is a complete circle. It goes through all parts of the circuit including the battery, and including the battery's electrolyte. A battery does not supply charges, it merely pumps them. Whenever electric charge flows into one terminal of a battery, an equal amount of charge must flow THROUGH the battery and back out through the other terminal. In a simple battery/bulb circuit, the charges flow around and around the circuit, going through both the battery and the bulb. The battery is a charge pump.


ELECTRIC ENERGY IS CARRIED BY INDIVIDUAL ELECTRONS? Wrong.

Some books teach that, in a simple battery/bulb circuit, the electrons deliver energy to the bulb, and then they return to the battery 'empty' and need to be re-filled with energy by the battery. Some books give an analogy with a circular train track full of freight cars waiting to be filled. This is wrong. The energy in electric circuits is not carried by individual electrons, it is carried by the circuit as a whole.

Here's an analogy which may help explain it: imagine a wheel that's free to spin. For example, turn a bicycle upside-down in your mind. Give the front tire a spin. When you spin the tire, your hand inject senergy into the whole wheel all at once. Now put your hand lightly against a different part of the tire so the spinning wheel is slowed and stopped by friction. Your hand gets hot. Your hand extracts energy from the entire wheel, all at once, and the whole wheel slows down. Finally, put one hand lightly against the tire while you use your other hand to keep the wheel spinning. Would it be right to tell students that the "Power" hand fills the rubber molecules with energy, that the molecules travel to the "friction" hand and dump their energy, then they return empty to the "power" hand and get refilled? No, of course not! If this were true then your "friction" hand wouldn't experience any friction until the magically "energized" rubber molecules made their way around the rim. Part of the wheel would be spinning while part would be de-energized and unmoving, and it would be really strange to watch!

A flashlight circuit is like our bicycle wheel. The electrons in the copper are like the rim of the wheel. The battery causes ALL the electrons in the loop of wire to begin moving, and so it injects energy into the WHOLE CIRCUIT all at once. As soon as the battery moves the electrons, the distant bulb lights up. The electrons moving into the bulb's filament are exactly the same as the ones moving out, the bulb doesn't change them or extract stored energy. Did your hand change the rubber tire as it rubbed on the bicycle wheel? No, it slowed the whole wheel down, it extracted energy from the whole wheel, and was heated by friction. Same thing with the bulb, it slows ALL the electrons down throughout the entire circuit, and in this way extracts energy from the whole circuit as it lights up.


BATTERIES STORE CHARGE, AND CHARGE FLOWS IN WIRES? No.

The word "charge" has more than one meaning, and the meanings contradict each other. The "charge" in a battery is enerry (chemical energy), while the "charge" that flows in wires is electron particles. The term "charge" refers to several different things: to net-charge, to quantities of charged particles, and to "charges" of energy. If you are not very careful while using the word "charge" in teaching, you might be spreading misconceptions.

For example, even when metals are totally neutral, they contain vast quantities of movable electrons. So, should we say that they contain zero charge because they are neutral? Or, should we say that they contain a very large amount of electric charge, because they are filled with electrons? Don't answer yet, because your answer might be inconsistant with how we describe capacitors (further below.)

Another: if I place an electron and a proton together, do I have twice as much charge as before, or do I have a neutral hydrogen atom with no charge at all? What I DO have is confusion. Misuse of "charge" makes descriptions of electric circuits seem complex and abstract, when the explanations are really just wrong.

Another: electric currents in wires are actually a motion of "neutralized" charge, where every electron has a proton nearby. If we teach that a wire is uncharged, and we ALSO teach that electric current is a flow of charge, how can anyone make sense of a situation where a wire has no charge at all, yet contains an enormous flow of charge? We could say "Oh, but electric currents are usually a flow of Uncharged Charge." WHAT? What would a student make of THAT statement? Can you see the problems that arise because of the word "charge?"

Another one: if you "charge" a battery, you cause an electric current in the electrolyte, and this electric current causes chemical reactions to occur upon the surfaces of the battery's plates. Chemical "fuel" acumulates, but charge does not. Chemical energy is stored in the battery, but electrical charge is not. When a battery is being "discharged", it's chemical fuel drives a process which pumps charge through the battery. The fuel will eventually be exhausted, but the total electric charge within the battery will never change!

Another one: if you "charge" a capacitor, you move charges from one plate to the other, and the number of charges within the device as a whole do not change. Or from an engineer's perspective, you drive charge THROUGH the capacitor, which causes potential across the plates to rise. But capacitors have exactly the same total charge within them whether they are "charged" or not! When we speak of "charging" capacitors, we've suddenly stopped talking about charge, and started talking about electrical energy. A "charged" capacitor has quite a bit more energy than an "uncharged" one (but exactly the same net-charge, and the same quantity of + and - particles.) This basic concept is very important in understanding simple circuitry, yet it is rarely taught. The misleading term "charge" stands in the way of understanding. I suspect that students are not the only ones being misled. Many teachers misunderstand simple physics, and they believe that the purpose of a capacitor is to store electric charge. Both capacitors and inductors (coils) store ENERGY, and neither one stores charge.


"STATIC ELECTRICITY" (CONTACT ELECTRIFICATION) IS CAUSED BY FRICTION? Wrong.

"Static electricity" is not caused by friction. It appears when two dissimilar insulating materials are placed into intimate contact and then separated. All that's required is the touching. For example, when adhesive tape is placed on an insulating surface and then peeled off, both the tape and the surface will become electrified. No rubbing was required. Or when a plastic wheel rolls across a rubber surface, both the surface and the wheel become electrified. Intimate contact is sufficient, and no rubbing is needed. Of course if one of the materials is rough or fibrous, it does not give a very large footprint of contact area. In this case the process of rubbing one material upon another can greatly increase the total contact area. But this rubbing is not the cause of electrification.

"STATIC ELECTRICITY" IS A BUILDUP OF ELECTRONS? Wrong.

It is not a buildup of anything, it is an IMBALANCE between QUANTITIES of positive and negative particles already present. During contact-electrification it is usually only the negative electrons which are moved. As negative particles are pulled away from the positive particles, equal and opposite areas of imbalance are created. In one place you'll have more protons than electrons, and this spot will have an overall positive charge. Elsewhere you'll have more electrons than protons, for an overall negative charge. You've not caused a "buildup", you've caused an imbalance, an un-cancelling, a separation. In fact, the science term for static electrification is CHARGE SEPARATION. The law of Conservation of Electric Charge requires that every time you create a region of negative charge, you must also create a region of positive charge. In other words you must create a separation of opposite charges.

"STATIC ELECTRICITY" IS ELECTRICITY WHICH IS STATIC? Wrong.

"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 phenomena 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 normal characteristics as it flows, so it does not stop being "static electricity" while it moves along very non-statically! In a high voltage electrical system, 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 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, 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 unmovingness. If you believe that "static" and "current" are opposite types of "electricity," you will forever be hopelessly confused about electricity in general.


ELECTRIC CURRENT IS A FLOW OF ENERGY? Wrong.

Electric current is a very slow motion of charged particles. On the other hand, electric energy is made of fields and it moves fast. Electric energy and electric particles are two different things. Electric energy can move in a direction opposite to that of the electric current. Electric energy can even move continuously forward in the same wire where the direction of the particle motion is alternating back and forth at high frequency. Electric energy is composed of electric and magnetic fields, and it exists in the space surrounding the wires. Electric current is very different, it is (usually) a flowing motion of electrons, and electrons are material particles, not energy particles. Electric current is a flow of matter, not of energy. When electric current exists in an electrolyte (in batteries, salt water, the earth, or in your body) it is a flow of charged atoms called ions, so there is no denying that it is a flow of material. Current is a matter flow, not an energy flow.

ELECTRIC POWER FLOWS FROM GENERATOR TO CONSUMER? Wrong.

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 (the current) is a type of substance. Doing otherwise 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 rate of flow of another thing; electric power is an energy current. Energy flows, but power never does, just as water flows but "current" never does.

This 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. Yet Watts have no physical, substance-like existence. The Joule is the fundamental unit, and the Watt is a unit of convenience. 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 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! They try to explain that joules are simply watt-seconds! (That's watts TIMES seconds, not watts per second.)


LIGHT AND RADIO WAVES TRAVEL AT 186,000 MILES PER SECOND? No.

They only travel at 186,000 miles per second while in a perfect vacuum. Light waves travel a bit slower in the air, and it travels LOTS slower when inside glass. Radio waves move much slower than 186,000 miles/sec when they travel within plastic-insulated coaxial cable. The term "speed of light" is misleading, because the complete term actually reads "speed of light in a vacuum." There actually is no set "speed of light," for light waves and light (and electrical energy) can travel at many different speeds depending on the medium through which the waves propagate.


ELECTROMAGNET COILS USE UP ENERGY TO MAKE MAGNETISM? Not right.

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) when charges flow in wires. But if the resistance is removed, the magnetic field can exist continuously without 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.

VOLTAGE

(under construction)

ELECTRIC CHARGES ONLY FLOW ON THE SURFACES OF WIRES? Wrong.

(under construction)

ELECTRIC CHARGES ARE INVISIBLE? No.

Electric charges are very visible, even though their motion is not. (under construction)

A "CONDUCTOR" IS A MATERIAL WHICH ALLOWS CHARGE TO PASS THROUGH IT? Not exactly.

The correct definition of the word "conductor" is different than the above. For example, a vacuum offers no barrier to charged particles, yet vacuum is an insulator. Vacuum allows charge to pass through, yet it is a terrible conductor. How can we straighten out this paradox? Easy: use the proper definition of "conductor." Fix it so it reads: "CONDUCTOR: a material which contains movable electric charges." If we place a Potential Difference across a vacuum, no electric current appears. This is sensible, since there are no movable charges in a vacuum, so there can be no electric current in a vacuum. If we place a voltage across a piece of metal or a puddle of salt water, an electric current will appear, since these substances are always full of movable charges, and 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. In salt water, the individual sodium ions and chloride ions are free to flow, and a voltage can push them so they flow as an electric current.

THE "TWO FLUIDS" THEORY WAS DISPROVED? Not exactly.

(under construction)

STORM CLOUDS ARE ELECTRIFIED BY FRICTION? No.

Some books claim that the separated charges in thunderstorms come about when clouds rub against each other, or when the falling rain rubs against the air. This is not correct. In fact, the true explanation for storm electrification is unknown. There are several possible explanations, but none of them has yet been accepted by scientists, and all the theories have problems. Here's one current theory:
In a mixture of rain and half-melted hail, the ice and water become oppositly electrified through contact. The large hail then falls faster than the small raindrops and spray. Two large regions appear in the cloud, one below that's made of hail, and one above that's made of rain. These regions contain opposite imbalances of electric charge.
So, what caused the clouds to become electrified? Contact between dissimilar materials, followed by wide separation of those materials.

BEN FRANKLIN'S KITE WAS STRUCK BY LIGHTNING? Never happened!

Many people believe that Ben Franklin's kite was hit by a lightning bolt, and this was how he proved that lightning was electrical. A number of books and even some encyclopedias say the same thing. They are wrong. When lightning strikes a kite, the spreading electric currents in the ground can kill anyone standing nearby, to say nothing of the person holding the string! So what did Franklin actually do? He showed that a kite would collect a tiny bit of electric charge out of the sky during a thunderstorm. Electric leakage through the air caused his kite and string to become electrified and so the hairs on the twine stood outwards. Twine is slightly conductive, so the imbalanced charge spread to all parts of the kite string. Franklin used the twine to electrify a metal key, and tiny sparks could then be drawn from the key. (He used a metal object because sparks cannot be directly drawn from the twine, it's not conductive enough.) This suggested that some stormclouds carry strong electrical net-charge. It IMPLIED that lightning was just a large electric spark.

The common belief that Franklin easily survived a lightning strike is not just wrong, it is dangerous: it may convince kids that it's OK to duplicate the kite experiment as long as they "protect" themselves by holding a silk ribbon. Make no mistake, Franklin's experiment was extremely dangerous, and if lightning had actually hit his kite, he certainly would have been killed.


ELECTRICITY IS MADE OF ELECTRONS? Wrong.

Electric current in metals is a flow of electrons. But there are many other conductors besides metals. Electric currents can also appear in electrolytes, or in plasma. When an electric current is flowing in a neon sign, electrons flow in one direction, while positively charged ATOMS flow in the other. Electric currents in electrolytes (such as wet dirt and human flesh) are flows of electrified atoms. When an electric current is passing through a battery, it is not made of moving electrons, it is made of moving atoms (ions.) A similar thing happens when a current passes through the earth, the ocean, or your body. All the electric currents in your brain and nerves are composed of moving sodium and potassium atoms. No electrons!