Titlebook: Mastering Electrical Engineering; Noel M. Morris Textbook 1985Latest edition Macmillan Publishers Limited 1985 electrical engineering.engi

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Alternating Current,As mentioned earlier, an alternating quantity is one which reverses its direction periodically, being in one direction (say the ‘positive’direction) at one moment and in the opposite direction (the ‘negative’ direction) the next moment. The frequency of alternations can be as low as once every few seconds or as high as once every few nanoseconds..

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Introduction to Single-Phase a.c. Circuits,In an a.c. circuit at normal power frequency, a resistance behaves in the same way as it does in a d.c. circuit. That is, . (Ohm’s law).

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The Transformer,In Chapter 7 (Electromagnetism) it was shown that.The above effects are involved in the process of ., illustrated in Figure 14.1, in which a changing alternating current in one coil of wire (the .) induces an e.m.f. in the second coil (the .). The general principle of operation is described below.

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Electrical Generators and Power Distribution,a permanent magnet was moved towards a coil of wire — see Figure 8.1 — an e.m.f. was induced in the coil. That is, the e.m.f. is induced by the relative movement between the magnetic field and the coil of wire. Lenz’s law allows us to predict the polarity of the induced e.m.f.

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