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Text 4. Electromagnetic induction and Faraday`s laws
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| Text 4. Electromagnetic induction and Faraday`s laws
«It is right that we should stand by and act on our principles; but not right to hold them in obstinate blindness, or retain them when proved to be erroneous» Michael Faraday PRE-READING Before we study the motion of an electromagnetic field in detail, let’s have some fun with electricity. In a small group discuss these problems and make notes of your main points. Then compare your notes. 1) How can you distinguish a magnet from a non-magnetized metal bar of the same size and material using no external means? 2. In 1722, George Graham discovered, by watching a compass needle, that the magnetic field of the Earth shows daily variations. Can you imagine why these variations occur? 2) If even knocking on a wooden door is an electric effect, we should be able to detect fields when doing so. Can you devise an experiment to check this? 3) Birds come to no harm when they sit on unprotected electricity lines. Nevertheless, one almost never observes any birds on tall, high voltage lines of 100 kV or more which transport power across longer distances. Why? 5. A PC or a telephone can communicate without wires, by using radio waves. Why are not these and other electrical appliances able to obtain their power via radio waves, thus eliminating power cables? Do you know the reasons? Active vocabulary Word Pronunciation Translation circuit, n. /ˈsɜːkɪt/ цепь, контур copper wire /ˈkɒpər waɪər/ медная проволока, провод deflect, v. /dɪˈflekt/ изменять направление, отклоняться от курса electrolysis, n. /ɪˌlekˈtrɒləsɪs/ электролиз electromotive /ɪˌlektrəˈməʊtɪv fɔːs/ электродвижущая сила force/emf 77 equation, n. /ɪˈkweɪʒən/ уравнение flux linkage /flʌksˈlɪŋkɪdʒ/ потокосцепление hence, adv. /hens/ следовательно, syn. therefore, thus induce, v. /ɪnˈdjuːs/ индуцировать, наводить induced current /ɪnˈdjuːst ˈkʌrənt/ индуцированный ток induction cooker /ɪnˈdʌkʃən ˈkʊkər/ индукционная плита needle, n. /ˈniːdl/ стрелка, syn. Index rotate, v. /rəʊˈteɪt/ вращать(ся) voltage, n. /ˈvəʊltɪdʒ/ электрическое напряжение жүктеу/скачать 1,14 Mb. Достарыңызбен бөлісу:
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