Electricity Misconceptions

ELECTRICITY MISCONCEPTIONS, William J. Beaty: http://amasci.com/miscon/elect.html

The Truth

When you connect a light bulb to a battery, Electrical Energy moves from the battery to the bulb. This is a one-way flow. The battery loses energy and the bulb gains it. Then the energy received by the bulb is turned into light. If this phenomenon is examined in great detail, we find that electrical energy is composed of waves traveling along columns of electrons inside the wires, and the energy itself is contained in electromagnetic fields connected to those electrons. We find that it travels 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 electrical energy did not travel in a circle. So, when you plug a lamp into a wall socket, you shouldn't imagine that the AC energy is a mysterious invisible entity traveling back and forth inside the wires. Instead you should think of AC energy as a mysterious invisible flow that comes out of the outlet, runs along the outside of both wires of the lamp cord, then it dives into the filament of the light bulb. Your electric company is sending out long "sausages" made of electrical energy. The wires are guiding them, and your appliances are absorbing them.

The Misconceptions

Many encyclopedias, dictionaries, and textbooks contain very clear statements about the nature of Electricity. They say this:

  • Electricity is a type of energy
  • Electric current is a flow of energy

The above statements are wrong. Yes, electrical energy does exist. However, this energy cannot be called "Electricity," since Coulombs of electricity are very different from Joules of electromagnetic energy.

Energy and charge are two different things, so they cannot both be the electricity. It's not too difficult to demonstrate the mistake. Below is a collection of simple facts which show that Electricity, the stuff that flows within copper wires, is not form of energy.

In a simple electric circuit, the electricity flows slowly in a complete circle, while the energy moves differently. The electrical energy flows rapidly across the circuit, going from the source to the load but not returning. The energy does not follow the circular flow of electricity; electricity and electrical energy are two different things.

No charges of electricity are gained or lost as the charges circulate within the wires, yet batteries create electrical energy from chemical energy, and light bulbs converts the electrical energy into light.

Electrical energy takes a rapid one-way path from battery to bulb and then leaves the circuit as light, while electricity flows slowly around (and around and around) a closed-loop path and none is lost. In a light bulb, charges of electricity flow through the filament and back out again. None are lost. This electricity enters the light bulb through one wire, and the same amount of electricity leaves through the other wire. Yet the energy doesn't act like this at all. The light bulb uses up the electric energy: the electrical energy flows into the bulb along both wires and is transformed into heat and light. The electrical energy does not come back out through the second wire and return to the battery.

In an AC system, the charges of electricity move back and forth over a distance shorter than a ten-thousandth of a millimeter. In other words, they sit inside the wires and vibrate. That's what "Alternating Current" or AC is all about. The electricity does not move forward at all (if it did, that would be a direct current or "DC.") Yet while these charges of electricity are wiggling back and forth, at the very same time the electrical energy moves forward rapidly. Only the electricity "alternates." The electrical energy does not; the energy flows continuously forwards as waves.

If this is confusing, consider sound waves which move through collections of air molecules. Electricity is like the air which is vibrating, while the electrical energy is like sound waves which fly through the air. Sound and air are two different things, just as energy and electricity are two different things.

In the above statements, I am using the word "electricity" in the way scientists have used it since Electricity was first investigated. I am using the word "electricity" to name the stuff that flows inside the wires; where a quantity of electrons is a quantity of electricity, and where a flow of electricity is called "an electric current." Why is this a trick? It's a trick because most people use the word "electricity" in a totally different way. They begin by defining the word "electricity" to mean electrical energy! Electric companies do this (think of kilowatt-hours of electricity). So do the science textbooks written for grades K-6. So do many dictionaries and encyclopedias. This causes endless confusion. Physicists try to tell us that the charges of electricity are not energy, and that a flow of charges is not a flow of energy. But then what is an electric current? Under the definition of "electricity" used by all the non-scientists, an electric current IS NOT a flow of electricity! Huh?

Confused? You SHOULD be confused. There's something wrong here. Note: my above statements about electricity and energy would be accepted by most scientists throughout history, including Ben Franklin, Michael Faraday, James C. Maxwell and Robert Millikan. I'm using the word electricity in the same manner as they did: electricity is the positive and negative "stuff" that's found in all electrons and protons. It is the "substance" that flows along inside of the wires. When it flows, these scientists would call it a "current of electricity." They'd say that any charged object has a "charge of electricity," and that electrons and protons are "particles of electricity." Without realizing it, the electric companies and the K-6 science textbooks are trying to re-define the original meaning of the word electricity. How can such a thing happen? I'll examine this, but first here are more facts about "electricity" as scientists use the word.

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.

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 and 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 students, 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.