Electricity is the flow of electrons. For more than a century we have been finding interesting ways to use electrical energy. An electromagnetic power source must either store a surplus of electrons or be able to use some force - usually magnetism - to force electrons to move back and forth in wavelike motions. Electromagnetic energy usually refers to systems that transfer electrical power wirelessly. Electromagnetic energy power sources have both advantages and disadvantages.
Electromagnetic energy is clean. It is not polluting like oil and coal energy sources, nor do we have to destroy the environment to get the raw materials -electrons are everywhere. It has no radioactive components that can explode violently or produce dangerous radioactivity for thousands of years. It also is renewable - we will never run out of electrons or magnetism. Besides being clean and renewable, electricity is versatile. We already know hundreds of ways to use electricity to cool, to heat and to drive motors of all sizes to perform all kinds of work. Electricity can be made to work on extremely small scales, such as in microchips. For packing a lot of information-processing power into a low energy-consuming package there is no other power source that even comes close.
The wireless transmission of electrical power is an idea that goes back to at least the early part of the 20th century. Nikola Tesla (a contemporary of Thomas Edison) worked on the project and discovered the chief disadvantage: It is not easy to achieve. This challenge remains the major disadvantage. Even if it was easy, there is another disadvantage that worries many people: is it safe. Most researchers have concluded that Radio Frequency (RF) waves--the proposed means of transmission--are completely safe and that RF has no affect on living tissue. Not everybody agrees.
New Developments
Electromagnetic power transmission is already a reality on a small scale. Joshua R. Smith, an Intel researcher in Seattle, has developed a device that collects power from ambient RF signals. These signals from radio and television broadcasts largely go to waste. The air is full of these signals. Only a small percent of the energy goes into activating the antennas of interested receivers - the rest goes into trees, houses, the ground or into outer space. Enough of this ambient energy already exists to power a large handheld calculator or an iPhone.
Chemical substance
Steam and liquid water are two different forms of the same chemical substance, water.
In chemistry, a chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. They can be solids, liquids or gases.
Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, salt (sodium chloride) and refined sugar (sucrose). However, simple or seemingly pure substances found in nature can in fact be mixtures of chemical substances. For example, tap water may contain small amounts of dissolved sodium chloride and compounds containing iron, calcium and many other chemical substances.
Chemical substances exist as solids, liquids, gases, or plasma and may change between these phases of matter with changes in temperature or pressure. Chemical reactions convert one chemical substance into another.
In geology, substances of uniform composition are called minerals, while physical mixtures (aggregates) of several minerals (different substances) are defined as rocks. Many minerals, however, mutually dissolve into solid solutions. An element is a chemical substance that is made up of a particular kind of atoms and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmutated into another element through a nuclear reaction. This is so, because all of the atoms in a sample of an element have the same number of protons, though they may be different isotopes, with differing numbers of neutrons.
There are about 120 known elements, about 80 of which are stable – that is, they do not change by radioactive decay into other elements. However, the number of chemical substances that are elements can be more than 120, because some elements can occur as more than a single chemical substance (allotropes). For instance, oxygen exists as both diatomic oxygen (O2) and ozone (O3). The majority of elements are classified as metals. These are elements with a characteristic lustre such as iron, copper, and gold. Metals typically conduct electricity and heat well, and they are malleable and ductile. Around a dozen elements, such as carbon, nitrogen, and oxygen, are classified as non-metals. Non-metals lack the metallic properties described above, they also have a high electronegativity and a tendency to form negative ions. Certain elements such as silicon sometimes resemble metals and sometimes resemble non-metals, and are known as metalloids.
Man’s Greatest Inventions
When people think of mankind’s history of inventions, many will mention things like the wheel, or fire. However, it can be argued that these were discoveries rather than inventions. For real inventions, you have to look to the later historical period. While there are a number of inventions that might be considered the "best," there are six that particularly stand out.
Compass. One of the most important early inventions was the compass. A compass allows a sailor to determine the direction of magnetic north, which made navigating easier. It was the invention of the compass that allowed Chinese navigators to take their ships on voyages as far as the coast of Africa, and possibly even to the west coasts of North and South America.
Steam Engine. While the ancient Greeks toyed with getting power from steam, the most they were able to achieve were simple toys like spinning spheres. It wasn’t until James Watt of Scotland invented the real stream engine in 1775 that this power could finally be harnessed for practicable purposes, from steamships to trains. As the motive force for electrical generation, steam transformed society in the 19th and 20th centuries, and helped spur technological improvement at an ever-increasing rate.
Light Bulb. Edison’s invention of the light bulb had far-reaching implications beyond the simple fact of being able to brighten a dark room with electricity. It led to changes in many of humanity’s fundamental habits. The 24-hour daily cycle became optional, and many people now took employment in businesses and factories running night shifts. Night life on the street became a bit less menacing, since cities could now make them almost as bright as day, which was a vast improvement over the weak gas lamps of the past.
Computer. Although inventors like Englishman Charles Babbage and his associate Ada Lovelace had worked on the concepts that underlay modern-day computers back in the 19th century, the technology did not yet exist to build the devices they envisioned. It was not until the invention of vacuum tubes that the power of the computer was realized. Modern computers came into being over a period of decades, and were the result breakthroughs made by many nations and individuals, such as the groundbreaking work of Alan Turing of England and American Jack Kilby’s invention of the integrated circuit. Modern computers contain far more calculating power than the early machines, and have affected almost every aspect of our live. One of the most obvious and pervasive effects that the computer has had can be seen in the rise of the The Internet as a primary means of communication and information dissemination.
Engineering Metals
Engineers will use a variety of different metals in their design work to accomplish a task. The various types of engineering, such as civil, environmental, chemical and electrical, will all require different metals depending on their various properties. Some commonly used metals or metal alloys include copper, gold, iron and steel. All of these materials are used in engineering for varying purposes due to their characteristic differences. These differences may include conductivity, malleability, hardness, corrosion or strength.
Copper
Copper is an elemental metal with an atomic number of 29, meaning it has 29 protons surrounding each atom. It is extremely malleable, which makes it valuable to engineers because it can form into almost any shape. Additionally, it is extremely conductive, which means it can transfer electricity and also heat well. This particular property makes it useful in electrical engineering, as it is used mostly for wiring. Copper is also commonly used in pipes because it prevents the growth of bacteria well. Copper will also corrode over time due to exposure to oxygen. To combat this corrosion, engineers have developed ways to combine copper with other materials; for example, a mixture of copper and zinc will form the stronger material known as brass.
Gold
Gold is a heavier metal with 79 protons around each atom. Gold is naturally yellow, while copper has a color like rust. Like copper, gold is a softer metal that is ductile, but when combined with other metals it can become stronger. Unlike any other engineering metal, gold uses a system known as carats to define its purity. If a sample of gold is said to be 24 carats, it has not been combined with any other metal. Also, unlike other metals, gold can be both found in nature and also synthesized in a laboratory. Gold can even be manufactured from seawater.
Iron
Iron is also an elemental metal found in the earth’s crust. Iron is valued for its magnetic properties, which are extremely useful in electrical engineering and also medical technology research. Its color is gray or silver, but it has a high corrosion rate, which makes pure iron difficult to use alone. Iron is often combined with other metals to create a stronger alloy, a trait shared by many elemental metals. Silicon is often added to iron to create cast iron. Adding carbon to iron results in steel.
Steel
Rather than an elemental metal, steel is an alloy produced by combining the elements iron and carbon. If the alloy contains a higher percentage of carbon, it will become harder. Despite its actual characterization as an alloy, steel is commonly referred to as an engineering metal due to its extremely useful properties. Steel is both malleable and quite strong. Once heated and quenched into shape, it is unlikely to break. Unlike copper, it resists corrosion, which allows it to be used in a wide range of engineering. Steel plays a role in every function of a human’s life, from silverware to building structures.
