The Science of Electricity
Greek philosopher, Thales of Miletus, known as one of the legendary Seven Wise Men, may have been the first human to study electricity, circa 600 B.C. By rubbing amber - fossilized tree resin - with fur, he was able to attract dust, feathers and other lightweight objects. These were the first experiments with electrostatics, the study of stationary electric charges or static electricity. In fact, the word electricity comes from the Greek word “elektron”, which means amber.
Though the history of electricity took small steps toward modernity for the next 2,500 years, our brief explanation of how electricity came to power the modern world begins with the man who is known as the father of the electric generator, Michael Faraday.
Faraday discovered that by wrapping two insulated coils of wire around an iron ring he could pass electricity from one coil to another. He used these early findings to create the “Faraday disk”, a dynamo -the first electrical generator capable of creating enough power to fuel industrial machinery which had to this point been driven by water wheels and animal power.
Faraday’s law of induction reveals that when a metal coil passes through a magnetic field, it will cause a voltage, or “electromotive force” to be “induced” - or produced. Faraday’s law is the basic principle upon which generators, electrical motors, and transformers work.
It’s fairly simple to understand, which to most outside of electrical engineering, makes it all the more difficult to understand. Rather, it is so simple, there seems as though there should be more to it. A magnetic field is that invisible force created by a magnet which, when placing a metal object near it, will pull that object towards it. Natural magnets, (known as lode stones, or magnetite) use this principle to hang out on refrigerators across the nation. What causes this natural magnetism is unclear to scientists though the leading theory is that lightning, which is surrounded by magnetic fields, has been magnetizing lodestones since the beginning of time through direct strikes on metal containing rock.
When a piece of metal like copper passes through a magnetic field (or vice-versa), the electrons in the metal begin to move. If you move that metal back and forth through the magnetic field, the electrons will also move back and forth. This is what creates “electromotive force” – the movement of electrons within the wire.
Everything is made of atoms. We all should know that by now, but most of us who slept through high school science class probably didn’t really get the concept of what an atom really is. To understand electricity, we have to understand electrons, and thus atoms. Atoms are small… so small that when they bind together, they can form an object which appears to us to be solid – like wood, rock, and metal. And of course, these things are solid… but scientifically, they are not. The atoms in them just happen to be packed so tightly that nothing can pass through them- including light. Different types of atoms bond together to form different types of materials. For instance, when the most basic atom – the hydrogen atom –combines with a lot of other hydrogen atoms, it forms the gas, hydrogen. Simple. When two different types of atoms are combined, more complex matter is created such as H2O (water) which has, of course, two hydrogen atoms combined with one oxygen atom.
Nearly all atoms are structured the same way. In the center (the nucleus), the subatomic particles protons and neutrons reside. Orbiting the nucleus are electrons. Neutrons are negatively charged components of an atom while electrons are positively charged. In their natural state, atoms don’t carry an electrical charge because atom carries the same number or neutrons as they do electrons, regardless of how many they have of each. But if the electrons are “moved around” –knock ed off their atom and into another- through some force – say a magnet, the atoms become electrically charged, temporarily. To maintain the charge, the movement has to continue.
Wood, glass, plastic, ceramic, air, cotton are all examples of materials whose electrons don’t move very well within their atoms. Because these electrons don’t move very easily, they can’t conduct electricity very well, if at all. These materials are known as electrical insulators. Most metals, however, have electrons that can be detached from their atoms and “zip around”. These are called free electrons. Atoms with “loose” or free electrons make it easy for electricity to flow through metals - they’re known as electrical conductors as they conduct electricity.
That’s the importance of understanding the atom in how electricity is created and the importance of Faraday’s discovery which led to the first practical application of electricity to move industrial machinery. Faraday’s discovery lead to the creation of dynamos.
A dynamo is an old term used to describe early electric generators that create DC power. The basic principle behind it, and current power generators, is that by rotating a copper wire between magnets, the electrons in the wire stay in motion and thus stay charged. Rotating the wire more quickly moves the electrons more quickly and thus creates more of a charge. A rotor in a generator is thus, obviously, referred to as such because it is the rotating, or the spinning part inside the magnetic field. The magnets are fixed – they don’t move, and are thus referred to as stators. In AC power generators however, stators contain the wires, wound around blocks (called windings) while the magnets do the spinning in the rotor.
In dynamos and simple generators, as the rotor rotates, the magnetic field it creates moves back and forth and thus, the electrons move back and forth, and in turn, the electrical current is constantly moving forward, then backward, or in reverse with every turn of the rotor. All this does is create an electromagnetic field of alternating currents. If you attached this to a light bulb, the bulb would flash on and off like a strobe light as the electricity is constantly changing direction. At the moment it changes direction, electricity ceases flowing, turning the bulb “off.”
To move the electricity forward through the wire, early inventors developed what is known as a commutator to create a direct current.
The commutator applies electric current to the windings. It reverses the direction of the electrical current each half turn, creating a steady rotating force which forces the current to flow in one direction. DC power was born from this simple solution in that commutators allowed the electricity being created in a generator to move forward through a copper wire line.
A commutator is an electrical switch that periodically reverses the current in an electric motor or electrical generator. Commutators enable motors to run on, and generators to produce, direct current instead of alternating current. More generally, commutators can be used to convert between direct and alternating current.
The Modern Mover
Commutators are relatively inefficient, and also require regular maintenance and component replacement. The true breakthrough in power generation was in utilizing the naturally occurring Alternating Current being generated without interruption of the flow of electricity back and forth.
The birth of the modern generator came from the breakthroughs of the polyphase system. By creating three offset magnetic fields, power can be driven at a constant state as at any given moment one of the three phases is always at or nearing its peak. This process is what drives modern power generators.