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BASIC ELECTRONIC COMPONENTS
It is the intention of this course to teach the fundamental operation of basic electronic components by comparison to drawings of equivalent mechanical parts. It must be understood that the mechanical circuits would operate much slower than their electronic counterparts and one-to-one correlation can never be achieved. The comparisons will, however, give an insight to each of the fundamental electronic components used in every electronic product.
1. Resistors
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The electronic component known as the resistor is best described as electrical friction. Pretend, for a moment, that electricity travels through hollow pipes like water. Assume two pipes are filled with water and one pipe has very rough walls. It would be easy to say that it is more difficult to push the water through the rough-walled pipe than through a pipe with smooth walls. The pipe with rough walls could be described as having more resistance to movement than the smooth one. Pioneers in the field of electronics thought electricity was some type of invisible fluid that could flow through certain materials easily, but had difficulty flowing through other materials. In a way they were correct since the movement of electrons through a material cannot be seen by the human eye, even with the best microscopes made. There is a similarity between the movement of electrons in wires and the movement of water in the pipes. For example, if the pressure on one end of a water pipe is increased, the amount of water that will pass through the pipe will also increase. The pressure on the other end of the pipe will be indirectly related to the resistance the pipe has to the flow of water. In other words, the pressure at the other end of the pipe will decrease if the resistance of the pipe increases. Electrons flow through materials when a pressure (called voltage in electronics) is placed on one end of the material forcing the electrons to “react” with each other until the ones on the other end of the material move out. Some materials hold on to their electrons more than others making it more difficult for the electrons to move. These materials have a higher resistance to the flow of electricity (called current in electronics) than the ones that allow electrons to move easily. Therefore, early experimenters called the materials insulators if they had very high resistance to electron flow and conductors if they had very little resistance to electron flow. Later materials that offered a medium amount of resistance were classified as semiconductors. When a person designs a circuit in electronics, it is often necessary to limit the amount of electrons or current that will move through that circuit each second. This is similar to the way a faucet limits the amount of water that will enter a glass each second. It would be very difficult to fill a glass without breaking it if the faucet had only two states, wide open or off. By using the proper value of resistance in an electronic circuit designers can limit the pressure placed on a device and thus prevent it from being damaged or destroyed
