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.