绝食
发表于 2025-3-27 00:20:42
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思考
发表于 2025-3-27 03:00:21
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..
课程
发表于 2025-3-27 05:45:04
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).
慢慢啃
发表于 2025-3-27 13:06:23
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.
洞穴
发表于 2025-3-27 16:59:23
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HAWK
发表于 2025-3-27 21:11:50
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transdermal
发表于 2025-3-28 00:29:30
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易于交谈
发表于 2025-3-28 03:27:55
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立即
发表于 2025-3-28 08:32:12
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.
温和女人
发表于 2025-3-28 12:51:18
Macmillan Masterhttp://image.papertrans.cn/m/image/625445.jpg