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1、Warming-up I. Can you point out the different components in the following picture? II. Do you know the meaning of the following phrases? 1. alternating voltage 2. electromotive force 3. electromagnetic induction,Unit 11 Transformer,下一页,返回,III. Talk about the different parts of a transformer .And the
2、 following questions you can use: Do you know what an ideal single-phase transformer consist of? Could you tell me how many kinds of coils are used in a transformer? Could you tell me the relation between the primary and secondary coil? What is the function of a transformer? Does a transformer have
3、losses? Text Comprehension Transformer A transformer cannot be called a machine, for it has no moving parts. It is designed for changing the alternating voltages and alternating currents by means of magnetic induction without any change of frequency.,Unit 11 Transformer,上一页,下一页,返回,A twowinding trans
4、former consists of two coils which are arranged so that the magnetic lines of force of one coil pass through the other. The alternating current in one coil induces an EMF in the other because of the alternations of the value of the coil current. To strengthen the magnetic field passing through the c
5、oils of a transformer. We generally use a closed core of iron. The coil to which the voltage is applied is known as the primary, while the one from which the induced voltage is obtained is known as the secondary. If the secondary has more turns than the primary, the transformer is called a stepup tr
6、ansformer in which the AC voltage of the secondary winding is higher than that applied to the primary winding. If the secondary has fewer turns than the primary, the transformer is called a stepdown transformer in which the AC voltage of the secondary winding is lower than that applied to the primar
7、y winding. In a wellbuilt transformer, the product of the secondary voltage and the secondary current is almost equal to that of the primary voltage and the primary current.,Unit 11 Transformer,上一页,下一页,返回,Using a transformer, it is possible for us to transform power at low voltage into an almost sim
8、ilar amount of power at high voltage, and vice versa. So the necessary voltage conversion is accomplished by use of transformers. The power output of a transformer is less than the power input because of unavoidable losses. These losses include resistance losses in the primary and secondary windings
9、 and losses in the core due to eddy current and hysteresis.,Unit 11 Transformer,上一页,下一页,返回,Vocabulary Transformer n. 变压器 transform v. 传输 design v. 设计 conversion n. 转化 frequency n. 频率 accomplish v. 完成 wind v. 缠绕 unavoidable adj. 不可避免的 coil n. 线圈 loss n. 损耗 strengthen v. 加强 eddy n. 回旋，旋转 apply v. 施加，应
10、用 hysteresis n. 滞后 Phrases and expressions alternating voltage 交变（流）电压 alternating current 交变(流)电压 by means of 以方式,Unit 11 Transformer,上一页,下一页,返回,magnetic induction 磁感应 core of iron 铁芯 a step-up transformer 升压变压器 a step-down transformer 降压变压器 vice versa 反之亦然 Notes 1. for 在这里是连词，引导原因状语从句。 2. a two wi
11、nding transformer 这里指由两个线圈组成的变压器，winding是分词做transformer 的定语。 3. The coil to which the voltage is applied is known as the primary, 这里primary 指primary coil,即初级线圈。 4. The coil to which the voltage is applied is known as the primary, while the one from which the induced voltage is obtained is known as t
12、he secondary. 本句中是介词加关系代词引导定于从句，修饰the coil.,Unit 11 Transformer,上一页,下一页,返回,5. A well-built transformer 意思是一个制作精良的变压器。 I Choose the right answer from A, B, and C according to the text. 【 】1.A transformer cannot be called a machine, for it has not _. A. moving parts B. moving elements C. moving electr
13、ons 【 】2. A transformer can be made according to the theory of _. A. alternating current. B. integrated circuits C. electromagnetic induction 【 】3. To strengthen the magnetic field passing through the coils of a transformer. We generally use. A. an air core. B. a closed core of iron. C. Not mentione
14、d.,Unit 11 Transformer,上一页,下一页,返回,【 】4. In a _ transformer, the losses is quite low. A. set-up B. set-down. C. well-built. 【 】5. Using a transformer, it is _for us to transform power at low voltage into an almost similar amount of power at high voltage, and vice versa. A possible B necessary C unnec
15、essary II True or false. 1. A transformer cannot be called a machine, for it has no moving parts. 2. The power output of a transformer is more than the power input because of unavoidable losses. 3. The transformer cannot be used to change the voltage of power. 4. The transformer can transform a low
16、voltage into a high voltage and vice versa. 5. If the secondary has fewer turns than the primary, the transformer is called a stepdown transformer.,Unit 11 Transformer,上一页,下一页,返回,III Translate the following sentences. 1. A twowinding transformer consists of two coils 2. If the secondary has more turns than the primary, the transformer is called a stepup transformer. 3. In a wellbuilt transformer, the
