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Semiconductors Semiconducting devices are at the heart of the microelectronic revolution that ushered in the information age. Table 27-2 compares the properties of silicon-a typical semiconductor-and copper-a typical metallic conductor. We see that silicon has many fewer charge carriers, a much higher resistivity, and a temperature coefficient of resistivity that is both large and negative. Thus, although the resistivity […]

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Power in Electric Circuits  A circuit consisting of a battery B that is connected by wires, which we assume have negligible resistance, to an unspecified conducting device. The device might be a resistor, a storage battery (a rechargeable battery), a motor, or some other electrical device. The battery maintains a potential difference of magnitude V across its own […]

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Microscopic View Of Ohm’s Law To find out why particular materials obey Ohm’s law, we must look into the details of the conduction process at the atomic level. Here we consider only conduction in metals, such as copper. We base our analysis on the free-electron model, in which we assume that the conduction electrons in the metal are […]

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Ohm’s Law As we just discussed in Section 27·4, a resistor is a conductor with a specified  resistance. It has that same resistance no matter what the magnitude and direction(polarity) of the applied potential difference. Other conducting devices, however, might have resistances that change with the applied potential difference.  shows how to distinguish such devices. A potential […]

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Resistance and Resistivity If we apply the same potential difference between the ends of geometrically similar rods of copper and of glass, very different currents result. The characteristic of the conductor that enters here is its electrical resistance. We determine the resistance between any two points of a conductor by applying a potential difference I’ those points and […]

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Current Density Sometimes we are interested in the current i in a particular conductor. At other times  we take a localized view and study the flow of charge through a cross section of the conductor at a particular point. To describe this flow, we can use the current density 7, which has the same direction as […]

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Current and Resistance The pride of Germany and a wonder of its time, the zeppelin Hindenburg-almost the length of three football  fields-was the largest flying machine that had ever been built. Although it was, kept aloft by’16 cells of highly flammable hydrogen gas, it made many trans-Atlantic trips without incident. In fact, German zeppelins, which all depended […]