Steam Engines
The introduction of an efficient steam engine in 1769 by Scottish engineer James Watt was one of the starting points of the Industrial Revolution. The steam engine allowed heat energy to be converted into mechanical work, and eventually, electric current. Steam engines propelled ships and trains, and provided energy for factory machinery. With the development of the steam engine, transportation took less time, and goods could be produced more quickly and efficiently.
Although the ancient Greeks are credited with the first use of steam-powered machines, the steam engine as it existed before 1769 was primitive. Prior to Watt's innovations, Englishmen Thomas Savery and Thomas Newcomen built a working steam engine that could be used for demonstrations, however, this engine was inefficient and could not be used for long periods of time. In the Savery-Newcomen engine, a piston in an open cylinder containing water was alternatively heated and cooled. The steam pressure forced the piston out, doing work; then the steam was vented, leading to greater pressure outside the cylinder, forcing the piston back in so the cycle could be repeated. Steam was lost in each cycle, however, and the water supply had to be constantly refilled. The efficiency of the engine was poor.
Watt made the engine more efficient with his idea of keeping the piston and cylinder at the same temperature as the steam entering the piston. Instead of alternately cooling and heating the water in the cylinder, the boiler producing the steam was constantly heated. Instead of venting the steam to the outside air, the steam was vented into an evacuated condenser, surrounded by water, so that the escaping steam would condense back into a liquid form. The water was then pumped back into the boiler to undergo the cycle again. In this way, the boiler did not have to be constantly refilled. The piston was connected to a system of driveshafts and gears to produce the desired mechanical work.
Modern steam engines use turbines to generate mechanical work. Steam from the boiling water strikes one side of a turbine, which acts like a fan blade. The turbine blades experience a torque and rotate, and the rotation can be connected to a series of gears and driveshafts similar to the piston engine.
Steam engines can be used to generate electricity, by using the principle of electromagnetic induction. Wire loops called commutators are attached to the rotating shaft of a steam engine. Strong permanent magnets are placed around the commutator, so that there is a changing magnetic flux through the wire loops. Changing magnetic flux through a wire loop produces an electric current in the loop (Faraday's laws).
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