Science of Electricity Basics
Everything Is Made of Atoms
In order to understand electricity, we need to know something about atoms. Everything in the universe is made of atoms — every star, every tree, every animal. The human body is made of atoms. Air and water are, too. Atoms are the building blocks of the universe. Atoms are so small that millions of them would fit on the head of a pin.
Atoms Are Made of Even Smaller Particles
The center of an atom is called the nucleus. It is made of particles called protons and neutrons. The protons and neutrons are very small, but electrons are much, much smaller. Electrons spin around the nucleus in shells a great distance from the nucleus. If the nucleus were the size of a tennis ball, the atom would be the size of the Empire State Building. Atoms are mostly empty space.
If you could see an atom, it would look a little like a tiny center of balls surrounded by giant invisible bubbles (or shells). The electrons would be on the surface of the bubbles, constantly spinning and moving to stay as far away from each other as possible. Electrons are held in their shells by an electrical force.
The protons and electrons of an atom are attracted to each other. They both carry anelectrical charge. Protons have a positive charge (+) and electrons have a negative charge (-). The positive charge of the protons is equal to the negative charge of the electrons. Opposite charges attract each other. An atom is in balance when it has an equal number of protons and electrons. The neutrons carry no charge and their number can vary.
The number of protons in an atom determines the kind of atom, or element, it is. An element is a substance consisting of one type of atom (the Periodic Table shows all the known elements), all with the same number of protons. Every atom of hydrogen, for example, has one proton, and every atom of carbon has six protons. The number of protons determines which element it is.
Electricity Is the Movement of Electrons Between Atoms
Electrons usually remain a constant distance from the nucleus in precise shells. The shell closest to the nucleus can hold two electrons. The next shell can hold up to eight. The outer shells can hold even more. Some atoms with many protons can have as many as seven shells with electrons in them.
The electrons in the shells closest to the nucleus have a strong force of attraction to the protons. Sometimes, the electrons in an atom's outermost shells do not. These electrons can be pushed out of their orbits. Applying a force can make them move from one atom to another. These moving electrons are electricity.
Static Electricity Exists in Nature
Lightning is a form of electricity. It is electrons moving from one cloud to another or jumping from a cloud to the ground. Have you ever felt a shock when you touched an object after walking across a carpet? A stream of electrons jumped to you from that object. This is called static electricity.
Have you ever made your hair stand straight up by rubbing a balloon on it? If so, you rubbed some electrons off the balloon. The electrons moved into your hair from the balloon. They tried to get far away from each other by moving to the ends of your hair. They pushed against each other and made your hair move — they repelled each other. Just as opposite charges attract each other, like charges repel each other.
Magnets and Electricity
Magnetic Field Around a Bar Magnet
Source: National Energy Education Development Project (Public Domain)
The spinning of the electrons around the nucleus of an atom creates a tiny magnetic field. Most objects are not magnetic because their electrons spin in different, random directions, and cancel out each other.
Magnets are different; the molecules in magnets are arranged so that their electrons spin in the same direction. This arrangement of atoms creates two poles in a magnet, a North-seeking pole and a South-seeking pole.
Magnets Have Magnetic Fields
The magnetic force in a magnet flows from the North pole to the South pole. This creates amagnetic field around a magnet.
Have you ever held two magnets close to each other? They don't act like most objects. If you try to push the South poles together, they repel each other. Two North poles also repel each other.
Turn one magnet around, and the North (N) and the South (S) poles are attracted to each other. Just like protons and electrons — opposites attract.
Magnetic Fields Can Be Used To Make Electricity
Properties of magnets can be used to make electricity. Moving magnetic fields can pull and push electrons. Metals such as copper have electrons that are loosely held. So electrons in copper wires can easily be pushed from their shells by moving magnets.
By using moving magnets and copper wire together, electric generators create electricity. Electric generators essentially convert kinetic energy (the energy of motion) into electrical energy.
Batteries, Circuits, & Transformers
Batteries Produce Electricity
Source: National Energy Education Development Project (Public Domain)
A battery produces electricity using two different metals in a chemical solution. A chemical reaction between the metals and the chemicals frees more electrons in one metal than in the other. One end of the battery is attached to one of the metals; the other end is attached to the other metal.
The end that frees more electrons develops a positive charge and the other end develops a negative charge. If a wire is attached from one end of the battery to the other, electrons flow through the wire to balance the electrical charge.
A load is a device that does work or performs a job. If a load –– such as a light bulb –– is placed along the wire, the electricity can do work as it flows through the wire. Electrons flow from the negative end of the battery through the wire to the light bulb. The electricity flows through the wire in the light bulb and back to the positive end of the battery.
Electricity Travels in Circuits
Electricity travels in closed loops, or circuits. It must have a complete path before the electrons can move. If a circuit is open, the electrons cannot flow. When we flip on a light switch, we close a circuit. The electricity flows from an electric wire, through the light bulb, and back out another wire.
When we flip the switch off, we open the circuit. No electricity flows to the light. When we turn a light switch on, electricity flows through a tiny wire in the bulb. The wire gets very hot. It makes the gas in the bulb glow. When the bulb burns out, the tiny wire has broken. The path through the bulb is gone.
When we turn on the TV, electricity flows through wires inside the TV set, producing pictures and sound. Sometimes electricity runs motors — in washers or mixers. Electricity does a lot of work for us many times each day.
Source: National Energy Education Development Project (Public Domain)
Transformers Help To Move Electricity Efficiently Over Long Distances
To solve the problem of sending electricity over long distances, William Stanley developed a device called a transformer. The transformer allowed electricity to be efficiently transmitted over long distances. This increased delivery range made it possible to supply electricity to homes and businesses located far from the electric generating plant.
The electricity produced by a generator travels along cables to a transformer, which changes electricity from low voltage to high voltage. Electricity can be moved long distances more efficiently using high voltage. Transmission lines are used to carry the electricity to a substation. Substations have transformers that change the high voltage electricity into lower voltage electricity. From the substation, distribution lines carry the electricity to homes, offices, and factories, which require low voltage electricity.
Measuring Electricity
Electricity Is Measured in Watts and Kilowatts
A Residential Electricity Meter
Source: Stock photography (copyrighted)
Electricity is measured in units of power called watts. It was named to honor James Watt, the inventor of the steam engine. One watt is a very small amount of power. It would require nearly 750 watts to equal one horsepower.
A kilowatt is the same as 1,000 watts.
Electricity Use Over Time Is Measured in Kilowatthours
A kilowatthour (kWh) is equal to the energy of 1,000 watts working for one hour. The amount of electricity a power plant generates or a customer uses over a period of time is measured in kilowatthours (kWh). Kilowatthours are determined by multiplying the number of kilowatts required by the number of hours of use.
For example, if you use a 40-watt light bulb for 5 hours, you have used 200 watthours, or 0.2 kilowatthours, of electrical energy. See EIA's Energy Calculator section to learn more about converting units.
How Electricity is Generated
How Electricity Is Generated
Turbine Generator
Source: adapted from Energy For Keeps (Public Domain)
A generator is a device that converts mechanical energy into electrical energy. The process is based on the relationship between magnetism and electricity. In 1831, scientist Michael Faraday discovered that when a magnet is moved inside a coil of wire, electrical current flows in the wire.
A typical generator at a power plant uses an electromagnet — a magnet produced by electricity — not a traditional magnet. The generator has a series of insulated coils of wire that form a stationary cylinder. This cylinder surrounds a rotary electromagnetic shaft. When the electromagnetic shaft rotates, it induces a small electric current in each section of the wire coil. Each section of the wire becomes a small, separate electric conductor. The small currents of individual sections are added together to form one large current. This current is the electric power that is transmitted from the power company to the consumer.
An electric utility power station uses either a turbine, engine, water wheel, or other similar machine to drive an electric generator — a device that converts mechanical or chemical energy to electricity. Steam turbines, internal-combustion engines, gas combustion turbines, water turbines, and wind turbines are the most common methods to generate electricity.
Steam turbine power plants powered by coal and nuclear energy produce about 70% of the electricity used in the United States. These plants are about 35% efficient. That means that for every 100 units of primary heat energy that go into a plant, only 35 units are converted to useable electrical energy.
