Sunday, December 13, 2009
Nowadays, the mobile phone is so important to us that it’s hard to think of life without it. However, they're a relatively new invention. This article explores the history of the mobile phone & questions what the future holds for it.
On 3 April 1973, Dr Martin Cooper, who was a Motorola employee, placed a call to rival Joel Engel, who was head of research at AT&T. Doctor Martin made the call while he was walking the streets of New York & did so through the first Motorola DynaTAC prototype in front of journalists.
The earliest mobile telephones were dubbed first generation telephones, often referred to as 1-G. These devices were the very first real mobile telephones, although they were then known as cellular mobile radiophones, & were based on analogue signalling. The analogue signal was the main difference between these first generation mobile telephones & their second generation cousins, which came out a few years later.
Second generation (2G) mobile phones were first released in the nineties. Unlike 1-G phones that were analogue, 2G phones use digital signalling to provide voice services & for text messaging & WAP internet access.
Some of the benefits of 2G phones are that they use lower radio signals, which require less battery power. This means that phones lasts a lot longer between charges, so batteries - & therefore the phones themselves - can be made littler. As well as this, 2G phones offer more privacy. Indeed, digital cellular calls are much harder to eavesdrop on than 1G phone calls.
The name 2.5G is used to refer to the phone technology that is post 2G, but not quite 3G. However, while the terms 2G & 3G are officially defined, the term 2.5G is not. In fact, this term was invented for marketing purposes only.
The earliest pre commercial 3G mobile phone network was launched in Japan in May 2001. Later, 3-G was released commercially in Japan on October 1 2001.
3G is the third generation of mobile phone standards and technology, which succeeded 2G mobile phone technology. The birth of 3-G technologies enabled network operators such as orange to offer their users a bigger range of advanced services. This includes broadband internet, as well as high tech video calls.
Despite the success of 3G, there's also been some complaints about it. These include criticism over the cost of 3G phones, as well as concerns over the lack of network coverage these phones get because it's still a pretty new service.
Ever since the launch of 3G mobile phone technology, people have been talking about 4-G. 4-G technology will signify the future of mobile telephones, creating the most sophisticated handsets & best services to date.
What is Forensic Science?Forensic science is a scientific method of gathering and examining evidence. Crimes are solved with the use of pathological examinations that gather fingerprints, palm prints, footprints, tooth bite prints, blood, hair and fiber samples. Handwriting and typewriting samples are studied, including all ink, paper, and typography. Ballistics techniques are used to identify weapons as well as voice identification techniques are used to identify criminals.
History of Forensic ScienceThe first recorded application of medical knowledge to the solution of crime. In the 1248 Chinese book Hsi DuanYu or the Washing Away of Wrongs, ways to distinguish between death by drowning or death by strangulation were described.
Italian doctor, Fortunatus Fidelis is recognized as being the first person to practice modern forensic medicine, beginning in 1598. Forensic medicine is the "application of medical knowledge to legal questions." It became a recognized branch of medicine in the early 19th century.
|18th century - Oxen and horses for power, crude wooden plows, all sowing by hand, cultivating by hoe, hay and grain cutting with sickle, and threshing with flail|
|1776-99||1790's - Cradle and scythe introduced |
1793 - Invention of cotton gin
1794 - Thomas Jefferson's moldboard of least resistance tested
1797 - Charles Newbold patented first cast-iron plow
|1800||1819 - Jethro Wood patented iron plow with interchangeable parts |
1819-25 - U.S. food canning industry established
|1830||1830 - About 250-300 labor-hours required to produce 100 bushels (5 acres) of wheat with walking plow, brush harrow, hand broadcast of seed, sickle, and flail |
1834 - McCormick reaper patented
1834 - John Lane began to manufacture plows faced with steel saw blades
1837 - John Deere and Leonard Andrus began manufacturing steel plows
1837 - Practical threshing machine patented
|1840||1840's - The growing use of factory-made agricultural machinery increased farmers' need for cash and encouraged commercial farming |
1841 - Practical grain drill patented
1842 - First grain elevator, Buffalo, NY
1844 - Practical mowing machine patented
1847 - Irrigation begun in Utah
1849 - Mixed chemical fertilizers sold commercially
|1850||1850 - About 75-90 labor-hours required to produce 100 bushels of corn (2-1/2 acres) with walking plow, harrow, and hand planting |
1850-70 - Expanded market demand for agricultural products brought adoption of improved technology and resulting increases in farm production
1854 - Self-governing windmill perfected
1856 - 2-horse straddle-row cultivator patented
|1860||1862-75 - Change from hand power to horses characterized the first American agricultural revolution |
1865-75 - Gang plows and sulky plows came into use
1868 - Steam tractors were tried out
1869 - Spring-tooth harrow or seedbed preparation appeared
|1870|| 1870's - Silos came into use |
1870's - Deep-well drilling first widely used
1874 - Glidden barbed wire patented
1874 - Availability of barbed wire allowed fencing of rangeland, ending era of unrestricted, open-range grazing
|1880||1880 - William Deering put 3,000 twine binders on the market |
1884-90 - Horse-drawn combine used in Pacific coast wheat areas
|1890||1890-95 - Cream separators came into wide use |
1890-99 - Average annual consumption of commercial fertilizer: 1,845,900 tons
1890's - Agriculture became increasingly mechanized and commercialized
1890 - 35-40 labor-hours required to produce 100 bushels (2-1/2 acres) of corn with 2-bottom gang plow, disk and peg-tooth harrow, and 2-row planter
1890 - 40-50 labor-hours required to produce 100 bushels (5 acres) of wheat with gang plow, seeder, harrow, binder, thresher, wagons, and horses
1890 - Most basic potentialities of agricultural machinery that was dependent on horsepower had been discovered
|1900||1900-1909 - Average annual consumption of commercial fertilizer: 3,738,300 |
1900-1910 - George Washington Carver, director of agricultural research at Tuskegee Institute, pioneered in finding new uses for peanuts, sweet potatoes, and soybeans, thus helping to diversify southern agriculture.
|1910||1910-15 - Big open-geared gas tractors came into use in areas of extensive farming |
1910-19 - Average annual consumption of commercial fertilizer: 6,116,700 tons
1915-20 - Enclosed gears developed for tractor
1918 - Small prairie-type combine with auxiliary engine introduced
|1920||1920-29 - Average annual consumption of commercial fertilizer: 6,845,800 tons |
1920-40 - Gradual increase in farm production resulted from expanded use of mechanized power
1926 - Cotton-stripper developed for High Plains
1926 - Successful light tractor developed
|1930||1930-39 - Average annual consumption of commercial fertilizer: 6,599,913 tons |
1930's - All-purpose, rubber-tired tractor with complementary machinery came into wide use
1930 - One farmer supplied 9.8 persons in the United States and abroad
1930 - 15-20 labor-hours required to produce 100 bushels (2-1/2 acres) of corn with 2-bottom gang plow, 7-foot tandem disk, 4-section harrow, and 2-row planters, cultivators, and pickers
1930 - 15-20 labor-hours required to produce 100 bushels (5 acres) of wheat with 3-bottom gang plow, tractor, 10-foot tandem disk, harrow, 12-foot combine, and trucks
|1940||1940-49 - Average annual consumption of commercial fertilizer: 13,590,466 tons |
1940 - One farmer supplied 10.7 persons in the United States and abroad
1941-45 - Frozen foods popularized
1942 - Spindle cottonpicker produced commercially
1945-70 - Change from horses to tractors and the adoption of a group of technological practices characterized the second American agriculture agricultural revolution
1945 - 10-14 labor-hours required to produce 100 bushels (2 acres) of corn with tractor, 3-bottom plow, 10-foot tandem disk, 4-section harrow, 4-row planters and cultivators, and 2-row picker
1945 - 42 labor-hours required to produce 100 pounds (2/5 acre) of lint cotton with 2 mules, 1-row plow, 1-row cultivator, hand how, and hand pick
|1950||1950-59 - Average annual consumption of commercial fertilizer: 22,340,666 tons |
1950 - One farmer supplied 15.5 persons in the United States and abroad
1954 - Number of tractors on farms exceeded the number of horses and mules for first times
1955 - 6-12 labor-hours required to produce 100 bushels (4 acres) of wheat with tractor, 10-foot plow, 12-foot role weeder, harrow, 14-foot drill and self-propelled combine, and trucks
Late 1950's - 1960's - Anhydrous ammonia increasingly used as cheap source of nitrogen, spurring higher yields
|1960||1960-69 - Average annual consumption of commercial fertilizer: 32,373,713 tons |
1960 - One farmer supplied 25.8 persons in the United States and abroad
1965 - 5 labor-hours required to produce 100 pounds (1/5 acre) of lint cotton with tractor, 2-row stalk cutter, 14-foot disk, 4-row bedder, planter, and cultivator, and 2-row harvester
1965 - 5 labor-hours required to produce 100 bushels (3 1/3 acres) of wheat with tractor, 12-foot plow, 14-foot drill, 14-foot self-propelled combine, and trucks
1965 - 99% of sugar beets harvested mechanically
1965 - Federal loans and grants for water/sewer systems began
1968 - 96% of cotton harvested mechanically
|1970||1970's - No-tillage agriculture popularized |
1970 - One farmer supplied 75.8 persons in the United States and abroad
1975 - 2-3 labor-hours required to produce 100 pounds (1/5 acre) of lint cotton with tractor, 2-row stalk cutter, 20-foot disk, 4 -row bedder and planter, 4-row cultivator with herbicide applicator, and 2-row harvester
1975 - 3-3/4 labor-hours required to produce 100 bushels (3 acres) of wheat with tractor, 30-foot sweep disk, 27-foot drill, 22-foot self-propelled combine, and trucks
1975 - 3-1/3 labor-hours required to produce 100 bushels (1-1/8 acres) of corn with tractor, 5-bottom plow, 20-foot tandem disk, planter, 20-foot herbicide applicator, 12-foot self-propelled combine, and trucks
|1980-90||1980's - More farmers used no-till or low-till methods to curb erosion|
1987 - 1-1/2 to 2 labor-hours required to produce 100 pounds (1/5 acre) of lint cotton with tractor, 4-row stalk cutter, 20-foot disk, 6-row bedder and planter, 6-row cultivator with herbicide applicator, and 4-row harvester
1987 - 3 labor-hours required to produce 100 bushels (3 acres) of wheat with tractor, 35-foot sweep disk, 30-foot drill, 25-foot self-propelled combine, and trucks
1987 - 2-3/4 labor-hours required to produce 100 bushels (1-1/8 acres) of corn with tractor, 5-bottom plow, 25-foot tandem disk, planter, 25-foot herbicide applicator, 15-foot self-propelled combine, and trucks
1989 - After several slow years, the sale of farm equipment rebounded
1989 - More farmers began to use low-input sustainable agriculture (LISA) techniques to decrease chemical applications
Advertisement for the Vitascope motion picture projector, marketed by the Edison Manufacturing Company even though it was invented by Thomas Armat and C. Francis Jenkins.
Edison was slow to develop a projection system (the Vitascope was a film projection system) at this time, since the single-user Kinetoscopes were very profitable. However, films projected for large audiences could generate more profits since less machines were needed in proportion to the number of viewers. Thus, others sought to develop their own projection systems.
One inventor who led the way was Woodville Latham who, with his sons, created the Eidoloscope projector which was presented publicly in April 1895. Dickson apparently advised the Lathams on their machine, offering technical knowledge, a situation which led to Dickson leaving Edison's employment on April 2, 1895.
Dickson formed the American Mutoscope Company in December of 1895 with partners Herman Casler, Henry Norton Marvin and Elias Koopman. The company, which eventually came to be known as the American Mutoscope and Biograph Company, soon became a major competitor to the Edison Company.
During the same period, C. Francis Jenkins and Thomas Armat developed a motion picture projection device which they called the Phantoscope. It was publicly demonstrated in Atlanta in September 1895 at the Cotton States Exposition. Soon after, the two parted ways, with each claiming sole credit for the invention.
Armat showed the Phantoscope to Raff and Gammon, owners of the Kinetoscope Company, who recognized its potential to secure profits in the face of declining kinetoscope business. They negotiated with Armat to purchase rights to the Phantoscope and approached Edison for his approval. The Edison Manufacturing Company agreed to manufacture the machine and to produce films for it, but on the condition it be advertised as a new Edison invention named the Vitascope.
The Vitascope's first theatrical exhibition was on April 23, 1896, at Koster and Bial's Music Hall in New York City. Other competitors soon displayed their own projection systems in American theaters, including the re-engineered Eidoloscope, which copied Vitascope innovations; the Lumière Cinématographe, which had already debuted in Europe in 1895; Birt Acres' Kineopticon; and the Biograph which was marketed by the American Mutoscope Company. The Vitascope, along with many of the competing projectors, became a popular attraction in variety and vaudeville theaters in major cities across the United States. Motion pictures soon became starring attractions on the vaudeville bill. Exhibitors could choose the films they wanted from the Edison inventory and sequence them in whatever order they wished.
The Edison Company developed its own projector known as the Projectoscope or Projecting Kinetoscope in November 1896, and abandoned marketing the Vitascope.
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.
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. Continue...How Electricity is Generated
Timeline - Electronic Inventions
Timeline - important events in the history.
Understanding - Electric Generators
Electric generators - What it is - how is a transformer used - how it is generated - how are turbines used - how is it measured.
Long article on several inventors connected to the field and their inventions.
An electromagnet is a device in which magnetism is produced by an electric current.
Magnetic Fields : History of Electromagnetism
Until 1820, the only magnetism known was that of iron magnets and of "lodestones", natural magnets of iron-rich ore. It was believed that the inside of the Earth was magnetized in the same fashion, and scientists were greatly puzzled when they found that the direction of the compass needle at any place slowly shifted, decade by decade, suggesting a slow variation of the Earth's magnetic field.
Electric Generator or Dynamo
Michael Faraday of England and American Joseph Henry separately built the first laboratory models of electric generator in 1832. Frenchmen, Hippolyte Pixii, France built a hand-driven model of an electric generator in 1833. American, Nikola Tesla built the first alternating-current generator in 1892.
The history of electronics began to evolve separately from the history of electricity late in the 19th century. The English physicist J.J. Thomson identified the electron by and the American physicist Robert A. Millikan measured its electric charge in 1909
The word phonograph was the trade name for Edison's device, which played cylinders rather than discs. The machine had two needles: one for recording and one for playback. When you spoke into the mouthpiece, the sound vibrations of your voice would be indented onto the cylinder by the recording needle. This cylinder phonograph was the first machine that could record and reproduce sound created a sensation and brought Edison international fame.
August 12, 1877, is the date popularly given for Edison's completion of the model for the first phonograph. It is more likely, however, that work on the model was not finished until November or December of that year, since he did not file for the patent until December 24, 1877. He toured the country with the tin foil phonograph, and was invited to the White House to demonstrate it to President Rutherford B. Hayes in April 1878.
In 1878, Thomas Edison established the Edison Speaking Phonograph Company to sell the new machine. He suggested other uses for the phonograph, such as: letter writing and dictation, phonographic books for blind people, a family record (recording family members in their own voices), music boxes and toys, clocks that announce the time, and a connection with the telephone so communications could be recorded.
• The History of the Cylinder Phonograph
Electricity and Lightbulb - History
Thomas Edison's greatest challenge was the development of a practical incandescent, electric light. Contrary to popular belief, he didn't "invent" the lightbulb, but rather he improved upon a 50-year-old idea. In 1879, using lower current electricity, a small carbonized filament, and an improved vacuum inside the globe, he was able to produce a reliable, long-lasting source of light. The idea of electric lighting was not new, and a number of people had worked on, and even developed forms of electric lighting. But up to that time, nothing had been developed that was remotely practical for home use. Edison's eventual achievement was inventing not just an incandescent electric light, but also an electric lighting system that contained all the elements necessary to make the incandescent light practical, safe, and economical. After one and a half years of work, success was achieved when an incandescent lamp with a filament of carbonized sewing thread burned for thirteen and a half hours.
There are a couple of other interesting things about the invention of the light bulb: While most of the attention was on the discovery of the right kind of filament that would work, Edison actually had to invent a total of seven system elements that were critical to the practical application of electric lights as an alternative to the gas lights that were prevalent in that day.
These were the development of:
The modern electric utility industry began in the 1880s. It evolved from gas and electric carbon-arc commercial and street lighting systems. On September 4, 1882, the first commercial power station, located on Pearl Street in lower Manhattan, went into operation providing light and electricity power to customers in a one square mile area; the electric age had begun. Thomas Edison's Pearl Street electricity generating station introduced four key elements of a modern electric utility system. It featured reliable central generation, efficient distribution, a successful end use (in 1882, the light bulb), and a competitive price. A model of efficiency for its time, Pearl Street used one-third the fuel of its predecessors, burning about 10 pounds of coal per kilowatt hour, a "heat rate" equivalent of about 138,000 Btu per kilowatt hour. Initially the Pearl Street utility served 59 customers for about 24 cents per kilowatt hour. In the late 1880s, power demand for electric motors brought the industry from mainly nighttime lighting to 24-hour service and dramatically raised electricity demand for transportation and industry needs. By the end of the 1880s, small central stations dotted many U.S. cities; each was limited to a few blocks area because of transmission inefficiencies of direct current (dc).
The success of his electric light brought Thomas Edison to new heights of fame and wealth, as electricity spread around the world. His various electric companies continued to grow until in 1889 they were brought together to form Edison General Electric. Despite the use of Edison in the company title however, he never controlled this company. The tremendous amount of capital needed to develop the incandescent lighting industry had necessitated the involvement of investment bankers such as J.P. Morgan. When Edison General Electric merged with its leading competitor Thompson-Houston in 1892, Edison was dropped from the name, and the company became simply General Electric.
Also see the History of the Lightbulb timeline.
Edison Motion Pictures - History
Thomas Edison's interest in motion pictures began before 1888, however, the visit of Eadweard Muybridge to his laboratory in West Orange in February of that year certainly stimulated his resolve to invent a camera for motion pictures. Muybridge proposed that they collaborate and combine the Zoopraxiscope with the Edison phonograph. Although apparently intrigued, Edison decided not to participate in such a partnership, perhaps realizing that the Zoopraxiscope was not a very practical or efficient way of recording motion. In an attempt to protect his future, he filed a caveat with the Patents Office on October 17, 1888, describing his ideas for a device which would "do for the eye what the phonograph does for the ear" -- record and reproduce objects in motion. He called it a "Kinetoscope," using the Greek words "kineto" meaning "movement" and "scopos" meaning "to watch."
One of Edison's first motion picture and the first motion picture ever copyrighted showed his employee Fred Ott pretending to sneeze. One problem was that a good film for motion pictures was not available. In 1893, Eastman Kodak began supplying motion picture film stock, making it possible for Edison to step up the production of new motion pictures. He built a motion picture production studio in New Jersey. The studio had a roof that could be opened to let in daylight, and the entire building was constructed so that it could be moved to stay in line with the sun.
C. Francis Jenkins and Thomas Armat invented a film projector called the Vitascope and asked Edison to supply the films and manufacture the projector under his name. Eventually, the Edison Company developed its own projector, known as the Projectoscope, and stopped marketing the Vitascope. The first motion pictures shown in a "movie theater" in America were presented to audiences on April 23, 1896, in New York City.
The Life of Thomas Edison (1847-1931)
• The Genius of Menlo Park - Biography
The Edison Laboratory, West Orange, New Jersey NPS Photo
Additional Biographies and History
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.
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.
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.
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.