中职电子专业英语第5章教学课件

1、正版可修改PPT课件(中职）电子专业英语第5章教学课件Warming-upI.Can you point out the difference of the following pictures?II.Do you know how to express the following formulas?R=UIR=pLSIII.Talk about Current in English. And the following patterns you can use: Do you know Ohms Law?Do you know who discovered “Ohms Law”Can you

2、 tell me how to express “Ohms Law”?Unit 5 Ohms Law下一页返回Could you tell me the relationship between the voltage, the current and the resistance?Can you tell me whether the resistance is constant or not in a circuit?Text ComprehensionOhms LawIn 1825, a German physicist called Ohm made the discovery tha

3、t a simple relationship exists between the three basic electric quantities, namely, resistance, current and voltage. He found that the resistance of a wire is constant, the current passing through is proportional to the potential difference maintained, as long as the temperature of the conductor rem

4、ains unchanged. Ohm also observed the fact that if the voltage remains the same, the greater the resistance, the smaller the current.Unit 5 Ohms Law上一页下一页返回Ohms two observations mentioned above can be put together in a simple statement that the current flowing in a circuit is directly proportional t

5、o the voltage and inversely proportional to the resistance. This statement is generally known as Ohms law.Its common to give a shorter form to Ohms law by using letters, the letter I meaning current, Vvoltage and Rresistance. Then Ohms law can be written: I = U / RThis relationship is considered to

6、be one of the most important in electricity. However, we should keep in mind that this relationship is true of metallic conductors.From Ohms law, we also know that the voltage across the ends of a wire is equal to the current times the resistance. Ohms law also provides the possibility of finding th

7、e resistance provided, the voltage and current are known.Unit 5 Ohms Law上一页下一页返回Examples:The voltage applied across the conductor is 6 V, and the current flowing through the conductor is 0.5 A, we can find the resistance of the conductor is 12(R= U/I=6 / 0.5=12).Vocabular 1. physicist n. 物理学家 6. mai

8、ntain vt. 维持，供给2. discovery n. 发现 7. directly adv. 直接地3. namely adv. 就是，换句话说 8. inversely adv. 逆向地，相反地Unit 5 Ohms Law上一页下一页返回4. constant adj. 恒定的，不变的 9. statement n. 叙述，语句 n. 恒量，常数10. possibility n. 可能性5.proportional adj. 成比例的 11. metallic adj. 金属的Phrases and expressions1. electric quantity电量2. be p

9、roportional to与成比例3. potential difference电势（电位）差4. be known as 被称为5. be equal to 等于Notes1. “the discovery that a simple relationship exists” that 引导一个同位语从句；下文 “observed the fact that if the voltage remains the same”that 引导的也是一个同位语从句。Unit 5 Ohms Law上一页下一页返回2. “the greater the resistance, the smaller

10、the current”这是形容词比较级的一种特殊用法， “the morethe more”(越越) 例如：The greater the quantity of impurities added, the higher will the conductivity of the semiconductor be. 掺杂杂质的数量越多，半导体的导电能力越强。3. “we should keep in mind that this relationship is true of metallic conductors”, “keep in mind” means “bear in mind” o

11、r “remember”; be true of: 适用于I Choose the right answer from A, B, and C according to the text. 【 】1.Ohms Law expresses the relationship between resistance, voltage and _.A. chargesB. currentC. potential difference【 】2. The resistance is related to _ in a circuit.A. currentB. temperature C. voltageUn

12、it 5 Ohms Law上一页下一页返回【 】3. In a circuit, if the voltage is constant, the greater the resistance, _ the current.A. the greaterB. the constant C. the smaller【 】4. The potential difference across the ends of a wire is equal to the product of _ and _.A. voltage, resistance B. current, resistance C. volt

13、age, current【 】5. The voltage across the conductor is 10 V, and the current flowing through the conductor is 2 A, we can find the resistance of the conductor is _.A 2B 10C 5II True or false.1. Ohms Law states the relationship between resistance, current and voltage.2. The resistance of the wire is c

14、hanging.Unit 5 Ohms Law上一页下一页返回3. The current through the wire is directly proportional to the potential difference across it.4. Ohms Law can be written U=IR. 5. Ohms Law isnt true of metallic conductors.III Translate the following sentences.1. As long as the temperature of the conductor remains unc

15、hanged, the current passing through it is proportional to the potential difference.2. If the voltage remains the same, the greater the resistance, the smaller the current.3. The current flowing in a circuit is directly proportional to the voltage and inversely proportional to the resistance.4. We should keep in mind that this relationship is true