TAILIEUCHUNG - Ebook Principles & practice of physics: Part 2
(BQ) Part 2 book "Principles & practice of physics" has contents: Alternating currents, semiconductors, RC and RLC series circuits, electric circuits, changing electric fields, changing magnetic fields, wave and particle optics,.and other contents. | QUANTITATIVE TOOLS CONCEPTS 32 Alternating currents AC circuits Semiconductors Diodes, transistors, and logic gates Reactance RC and RLC series circuits Resonance Power in AC circuits Electronics AlternAting currents I n the preceding chapter, we discussed electric circuits in which the current is steady. As noted in that chapter, the steady flow of charge carriers in one direction only is called direct current. Batteries and other devices that produce static electrical charge, such as van de Graaff generators, are sources of direct current. Although direct current has many uses, it has several limitations as well. For example, in order to produce substantial currents, direct-current sources must be quite large and are therefore cumbersome. More important, steady currents do not generate any electromagnetic waves, which can be used to transmit information and energy through space, as we saw in Chapter 30. Because of these and many other factors, most electric and electronic circuits operate with alternating currents (abbreviated AC)—currents that periodically change direction. The current provided by household outlets in the United States, for instance, alternates in direction, completing 60 cycles per second (that is, with a frequency of 60 Hz), and the currents in computer circuits change direction billions of times per second. It is no understatement to say that contemporary society depends on alternating currents. In this chapter we discuss the basics of both household currents and the electronics that lie at the heart of computers. Alternating currents Figure What happens when we connect an inductor to a charged capacitor? fully charged capacitor E inductor (a) Just before the inductor is connected to the charged capacitor, what type of energy is contained in the system comprising the two elements? (b) Once the two elements are connected to
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