Electricity - Electronics
Electricity is a form of energy involving the flow of electrons. All matter is made up of atoms, and an atom has a center, called a nucleus. The nucleus contains positively charged particles called protons and uncharged particles called neutrons. The nucleus of an atom is surrounded by negatively charged particles called electrons. The negative charge of an electron is equal to the positive charge of a proton, and the number of electrons in an atom is usually equal to the number of protons. When the balancing force between protons and electrons is upset by an outside force, an atom may gain or lose an electron. When electrons are "lost" from an atom, the free movement of these electrons constitutes an electric current. 
Electricity is a basic part of nature and it is one of our most widely used forms of energy. We get electricity, which is a secondary energy source, from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. Many cities and towns were built alongside waterfalls (a primary source of mechanical energy) that turned water wheels to perform work. Before electricity generation began slightly over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves. Beginning with Benjamin Franklin's experiment with a kite one stormy night in Philadelphia, the principles of electricity gradually became understood. In the mid-1800s, everyone's life changed with the invention of the electric light bulb. Prior to 1879, electricity had been used in arc lights for outdoor lighting. The lightbulb's invention used electricity to bring indoor lighting to our homes.Theory
An electric generator (Long ago, a machine that generated electricity was named "dynamo" today's preferred term is "generator".) is a device for converting mechanical energy into electrical energy. The process is based on the relationship between magnetism and electricity. When a wire or any other electrically conductive material moves across a magnetic field, an electric current occurs in the wire. The large generators used by the electric utility industry have a stationary conductor. A magnet attached to the end of a rotating shaft is positioned inside a stationary conducting ring that is wrapped with a long, continuous piece of wire. When the magnet rotates, it induces a small electric current in each section of wire as it passes. Each section of wire constitutes a small, separate electric conductor. All the small currents of individual sections add up to one current of considerable size. This current is what is used for electric power.
An electric utility power station uses either a turbine, engine, water wheel, or other similar machine to drive an electric generator or 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.
WHAT IS ELECTRICITY?
Electricity is a form of energy. Electricity is the flow of electrons. All matter is made up of atoms, and an atom has a center, called a nucleus. The nucleus contains positively charged particles called protons and uncharged particles called neutrons. The nucleus of an atom is surrounded by negatively charged particles called electrons. The negative charge of an electron is equal to the positive charge of a proton, and the number of electrons in an atom is usually equal to the number of protons. When the balancing force between protons and electrons is upset by an outside force, an atom may gain or lose an electron. When electrons are "lost" from an atom, the free movement of these electrons constitutes an electric current. Electricity is a basic part of nature and it is one of our most widely used forms of energy. We get electricity, which is a secondary energy source, from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. Many cities and towns were built alongside waterfalls (a primary source of mechanical energy) that turned water wheels to perform work. Before electricity generation began slightly over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves. Beginning with Benjamin Franklin's experiment with a kite one stormy night in Philadelphia, the principles of electricity gradually became understood. In the mid-1800s, everyone's life changed with the inventionof the electric light bulb. Prior to 1879, electricity had been used in arc lights for outdoor lighting. The lightbulb's invention used electricity to bring indoor lighting to our homes.
HOW IS A TRANSFORMER USED?
To solve the problem of sending electricity over long distances, George Westinghouse developed a device called a transformer. The transformer allowed electricity to be efficiently transmitted over long distances. This made it possible to supply electricity to homes and businesses located far from the electric generating plant.
Despite its great importance in our daily lives, most of us rarely stop to think what life would be like without electricity. Yet like air and water, we tend to take electricity for granted. Everyday, we use electricity to do many functions for us -- from lighting and heating/cooling our homes, to being the power source for televisions and computers. Electricity is a controllable and convenient form of energy used in the applications of heat, light and power.
Today, the United States (U.S.) electric power industry is organized to ensure that an adequate supply of electricity is available to meet all demand requirements at any given instant.
HOW IS ELECTRICITY GENERATED?
An electric generator is a device for converting mechanical energy into electrical energy. The process is based on the relationship between magnetism and electricity. When a wire or any other electrically conductive material moves across a magnetic field, an electric current occurs in the wire. The large generators used by the electric utility industry have a stationary conductor. A magnet attached to the end of a rotating shaft is positioned inside a stationary conducting ring that is wrapped with a long, continuous piece of wire. When the magnet rotates, it induces a small electric current in each section of wire as it passes. Each section of wire constitutes a small, separate electric conductor. All the small currents of individual sections add up to one current of considerable size. This current is what is used for electric power.
An electric utility power station uses either a turbine, engine, water wheel, or other similar machine to drive an electric generator or 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. Most of the electricity in the United States is produced in steam turbines. A turbine converts the kinetic energy of a moving fluid (liquid or gas) to mechanical energy. Steam turbines have a series of blades mounted on a shaft against which steam is forced, thus rotating the shaft connected to the generator. In a fossil-fueled steam turbine, the fuel is burned in a furnace to heat water in a boiler to produce steam.
Coal, petroleum (oil), and natural gas are burned in large furnaces to heat water to make steam that in turn pushes on the blades of a turbine. Did you know that coal is the largest single primary source of energy used to generate electricity in the United States? In 1998, more than half (52%) of the county's 3.62 trillion kilowatthours of electricity used coal as its source of energy.
Natural gas, in addition to being burned to heat water for steam, can also be burned to produce hot combustion gases that pass directly through a turbine, spinning the blades of the turbine to generate electricity. Gas turbines are commonly used when electricity utility usage is in high demand. In 1998, 15% of the nation's electricity was fueled by natural gas.
Petroleumcan also be used to make steam to turn a turbine. Residual fuel oil, a product refined from crude oil, is often the petroleum product used in electric plants that use petroleum to make steam. Petroleum was used to generate less than three percent (3%) of all electricity generated in U.S. electricity plants in 1998.
Nuclear power is a method in which steam is produced by heating water through a process called nuclear fission. In a nuclear power plant, a reactor contains a core of nuclear fuel, primarily enriched uranium. When atoms of uranium fuel are hit by neutrons they fission (split), releasing heat and more neutrons. Under controlled conditions, these other neutrons can strike more uranium atoms, splitting more atoms, and so on. Thereby, continuous fission can take place, forming a chain reaction releasing heat. The heat is used to turn water into steam, that, in turn, spins a turbine that generates electricity. Nuclear power is used to generate 19% of all the country's electricity.
Hydropower, the source for 9% of U.S. electricity generation, is a process in which flowing water is used to spin a turbine connected to a generator. There are two basic types of hydroelectric systems that produce electricity. In the first system, flowing water accumulates in reservoirs created by the use of dams. The water falls through a pipe called a penstock and applies pressure against the turbine blades to drive the generator to produce electricity. In the second system, called run-of-river, the force of the river current (rather than falling water) applies pressure to the turbine blades to produce electricity.
OTHER GENERATING SOURCES
Geothermal power comes from heat energy buried beneath the surface of the earth. In some areas of the country, magma (molten matter under the earth's crust) flows close enough to the surface of the earth to heat underground water into steam, which can be tapped for use at steam-turbine plants. This energy source generates less than 1% of the electricity in the country.
Solar power is derived from the energy of the sun. However, the sun's energy is not available full-time and it is widely scattered. The processes used to produce electricity using the sun's energy have historically been more expensive than using conventional fossil fuels. Photovoltaic conversion generates electric power directly from the light of the sun in a photovoltaic (solar) cell. Solar-thermal electric generators use the radiant energy from the sun to produce steam to drive turbines. Less than 1% of the nation's electricity is based on solar power.
Wind power is derived from the conversion of the energy contained in wind into electricity. Wind power like the sun, is usually an expensive source of producing electricity, and is used for less than 1% of the nation's electricity. A wind turbine is similar to a typical wind mill.
Biomass(wood, municipal solid waste (garbage), and agricultural waste, such as corn cobs and wheat straw, are some other energy sources for producing electricity. These sources replace fossil fuels in the boiler. The combustion of wood and waste creates steam that is typically used in conventional steam-electric plants. Biomass accounts for less than 1% of the electricity generated in the United States.
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.HOW IS ELECTRICITY MEASURED?
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 represents 1,000 watts. A kilowatt-hour (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 kW's required by the number of hours of use. For example, if you use a 40-watt light bulb 5 hours a day, you have used 200 watts of power, or .2 kilowatthours of electrical energy.
How Electric Motors and Generators Work
Electric vehicles rely exclusively on electric motors for propulsion, and hybrids use electric motors to assist their internal combustion engines for locomotion. But that's not all. These very motors can be, and are, used to generate electricity (through the process of regenerative braking) for charging these vehicles' onboard batteries. The most common question is: "How can that be ..
. how does that work?" Most folks understand that a motor is powered by electricity to do work—they see it everyday in their household appliances (washing machines, vacuum cleaners, food processors). But the idea that a motor can "run backwards," actually generating electricity rather than consuming it seems almost like magic. But once the relationship between magnets and electricity (electromagnetism) and the concept of conservation of energy is understood, the mystery disappears.Electromagnetism
Motor power and electricity generation begin with the property of electromagnetism—the physical relationship between a magnet and electricity. An electromagnet is a device that acts like a magnet, but its magnetic force is manifested and controlled by electricity. When wire made of conducting material (copper, for example) moves through a magnetic field, current is created in the wire (a rudimentary generator). Conversely, when electricity is passed through a wire that is wound around an iron core, and this core is in the presence of a magnetic field, it will move and twist (a very basic motor).Motor/Generators
Motor/generators are really one device that can run in two opposite modes. Contrary to what folks sometimes think, that does not mean that the two modes of the motor/generator run backwards from each other (that as a motor the device turns in one direction and as a generator, it turns the opposite direction). The shaft always spins the same way. The "change of direction" is in the flow of electricity. As a motor it consumes electricity (flows in) to make mechanical power, and as a generator, it consumes mechanical power to produce electricity (flows out).Electromechanical Rotation
Electric motor/generators are generally one of two types, either AC (Alternating Current) or DC (Direct Current) and those designations are indicative of the type of electricity that they consume and generate. Without getting into too much detail and clouding the issue, this is the difference: AC current changes direction (alternates) as it flows through a circuit. DC currents flows uni-directionally (stays the same) as it goes through a circuit. The type of current utilized is concerned mostly with the cost of the unit and its efficiency (An AC motor/generator is generally more expensive, but is also much more efficient). Suffice it to say that most hybrids and many larger all-electric vehicles use AC motor/generators—so that is the type we'll focus on in this explanation.An AC Motor/Generator Consists of 4 Main Parts:
- A shaft-mounted wire wound armature (rotor)
- A field of magnets that induce electrical energy stacked side-by-side in a housing (stator)
- Slip rings that carry the AC current to/from the armature
- Brushes that contact the slip rings and transfer current to/from the electrical circuit
The AC Generator in Action
The armature is driven by a mechanical source of power (for example, in commercial electric power production it would be a steam turbine). As this wound rotor spins, its wire coil passes over the permanent magnets in the stator and an electric current is created in the wires of the armature. But because each individual loop in the coil passes first the north pole then the south pole of each magnet sequentially as it rotates on its axis, the induced current continually, and rapidly, changes direction. Each change of direction is called a cycle, and it is measured in cycles-per-second or hertz (Hz). In the United States, the cycle rate is 60 Hz (60 times per second), while in most other developed parts of the world it is 50 Hz. Individual slip rings are fitted to each of the two ends of the rotor's wire loop to provide a path for the current to leave the armature. Brushes (which are actually carbon contacts) ride against the slip rings and complete the path for the current into the circuit to which the generator is attached.The AC Motor in Action
Motor action (supplying mechanical power) is in essence the reverse of generator action. Instead of spinning the armature to make electricity, current is fed by a circuit, through the brushes and slip rings and into the armature. This current flowing through the coil wound rotor (armature) turns it into an electromagnet. The permanent magnets in the stator repel this electromagnetic force causing the armature to spin. As long as electricity flows through the circuit, the motor will run.Electricity is one of the most widely used forms of energy used by humans throughout
the world. In early times many cities and towns were built alongside waterfalls (a primary source
of mechanical energy) that turned water wheels to perform work. Before the electricity
generation began slightly over 100 years ago, houses were lit with kerosene lamps, food was
cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves.
Most people do not stop to think what life would be like without electricity and tend to
take it for granted because it is always there. It does so many things for us such as lighting and
heating/cooling homes, powering televisions and computers.
Sources of Electricity
• Lightning, a form of static electricity, is electrons moving from one cloud to another or
from a cloud to the ground. An example of static electricity would be walking over a
carpet and touching an object and a stream of electrons jumped to you from that object.
• Magnets and Electricity, The spinning of the electrons around the nucleus of an atom
creates a tiny magnetic field. Most objects are not magnetic because the atoms are
arranged so that the electrons spin in different, random directions, and cancel out each
other. Magnets and wire are used together in electric generators.
• Batteries produce electricity using two different metals in a chemical solution. A
reaction between the metals and the chemical frees more electrons in one metal than in
the other. If a wire is attached to both ends of the battery and a light bulb, the electricity
flows lighting the bulb.
Electricity Travels in Circuits
Electricity travels in closed loops or circuits, to provide a complete path before the
electrons can move. If a circuit is open, the electrons cannot flow. When a light switch, is turned
on there is a complete a circuit and electricity flows through the circuit illuminating the light
bulb. When the light switch is shut off, the circuit is open and no electricity flows to the light
bulb. When a light switch is turned on, electricity flows through a tiny wire in the bulb and it
glows. When the tiny wire has broken, the path through the bulb is gone. 2
How Electricity is Generated
Most of the electricity in North America is produced in steam turbines. A turbine
converts the energy of a moving fluid (liquid or gas) to mechanical energy. Steam turbines have
a series of blades mounted on a shaft against which steam is forced, thus rotating the shaft
connected to the generator.
• Coal, petroleum (oil), and natural gas are burned in large furnaces to heat water to make
steam that pushes on the blades of a turbine. Coal is the largest single primary source of
energy used to generate electricity in the North America.
• Hydropower, the source of most electricity generated, consists of a process where
flowing water is used to spin a turbine connected to a generator. There are two basic
types of hydroelectric systems: one where flowing water from a reservoir is used, and the
other the force of the water current applies pressure to the turbine blades.
• Nuclear is a method in which steam is produced by heating water through a process
called nuclear fission. When atoms of uranium fuel are hit by neutrons they fission (split),
releasing heat and form a chain reaction releasing heat that spins a turbine to generate
electricity.
• Wind Power is derived from the conversion of the energy contained in wind into
electricity. Wind power turbines are similar to a typical wind mill.
The Transformer - Moving Electricity
The transformer allows electricity to be sent over long distances. This 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. Transmission lines carry the electricity to a
substation which sends the electricity to homes, offices and factories.
Summary
1. Fuel (coal, oil natural gas or nuclear) is
burned in a large boiler.
2. Boiler, and its walls are made up of tubes
that carry water.
3. Water, the fuel gives off its chemical heat
energy to the tube metal of the boiler. The 3
heat travels by conduction through the walls and is absorbed by the water. The water
temperature increases until it is finally transformed into
4. Steam now under considrable pressure and at a very high temperature is piped to a
5. Turbine where mechanical energy is produced. The steam strikes the blades of the
turbine and spins them revolvong the turbine shaft. The spinning shaft is connected to the
6. Rotor, a large electromagnet. A wire coil called the
7. Stator surrounds the rotor, as the rotor revolves within the stator, a flow of electrons, or
8. Electricity is produced. The electricity is then collected at a predetermined voltage and
frquency and distributed by an elaborate
9. Transmission and Distribution system. After the steam passes through the turbine, it is
led into a steam
10. Condensor, the hot steam is condened back into water and returned to the boiler to begin
the cycle again.
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