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Reading II SkimmingTask 6I. Read the text and complete the sentences according to the text.
1. Electromagnetism is responsible for … 2. James Clerk Maxwell was the first to describe… 3. In the 19th century electricity and magnetism … 4. However, electric and magnetic forces … 5. Electric forces are produced by … 6. Magnetic forces are produced by … 7. Electric and magnetic fields are regions … 8. Michael Faraday discovered that … 9. James Clerk Maxwell deduced that … 10. The science of electricity is concerned with … 11. The fundamental concepts of the science of electricity are .. 12. A common problem in electricity is … Electromagnetism is responsible for interactions between charged particles that occur because of their charge, and for the emission and absorption of photons (electromagnetic radiation). The phenomena of electricity and magnetism are consequences of this force, and the relationships between them were first described by James Clerk Maxwell in the 1860s. The physical description of electromagnetism has since been combined with quantum mechanics into the theory of quantum electrodynamics. The electromagnetic force is about 1036 times as strong as the gravitational force. Electricity and magnetism were long thought to be separate forces. It was not until the 19th century that they were finally treated as interrelated phenomena. In 1905 Albert Einstein’s special theory of relativity established beyond doubt that both are aspects of one common phenomenon. At a practical level, however, electric and magnetic forces behave quite differently and are described by different equations. Electric forces are produced by electric charges either at rest or in motion. Magnetic forces, on the other hand, are produced only by moving charges and act solely on charges in motion. Electric and magnetic forces can be detected in regions called electric and magnetic fields. These fields can exist in space far from the charge or current that generated them. Remarkably, electric fields can produce magnetic fields and vice versa, independent of any external charge. A changing magnetic field produces an electric field, as the English physicist Michael Faraday discovered in work that forms the basis of electric power generation. Conversely, a changing electric field produces a magnetic field, as the Scottish physicist James Clerk Maxwell deduced. An important aspect of electromagnetism is the science of electricity, which is concerned with the behaviour of aggregates of charge, including the distribution of charge within matter and the motion of charge from place to place. Different types of materials are classified as either conductors or insulators on the basis of whether charges can move freely through their constituent matter. Electric current is the measure of the flow of charges; the laws governing currents in matter are important in technology, particularly in the production, distribution, and control of energy. The concept of voltage, like those of charge and current, is fundamental to the science of electricity. Voltage is a measure of the propensity of charge to flow from one place to another; positive charges generally tend to move from a region of high voltage to a region of lower voltage. A common problem in electricity is determining the relationship between voltage and current or charge in a given physical situation. Date: 2016-01-03; view: 1071
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