tailieunhanh - Tiếng anh chuyên ngành điện - điện tử - ĐH Sư Phạm Kỹ Thuật Hưng Yên

English for Electrical and Electronic Engineering - Tiếng anh chuyên ngành điện - điện tử dùng cho sinh viên đại học sư phạm kỹ thuật và sinh viên chuyên ngành điện - điện tử tham khảo học tập. | BỘ GIÁO DỤC VÀ ĐÀO TẠO TRƯỜNG ĐẠI HỌC Sư PHẠM KỸ THUẬT HƯNG YÊN to Elclđ M teliỀ tojiiwlj TIẾNG ANH CHUYÊN NGÀNH ĐIỆN-ĐIỆN TỬ 8-2006 SECTION OF FOREIGN LANGUAGE CONTENT page Unit 1 Conductors insulators and semiconductors 1 Unit 2 Circuit elements 8 Unit 3 DC motor 17 Unit 4 Electrical ignition 28 Unit 5 Moving coil 31 Unit 6 Process control systems 38 Unit 7 Semiconductor 45 Unit 8 Cathode ray tube 52 Unit 9 Alarm system 59 Unit 10 Music centre 66 Chú giải sơ đồ mạch 74 Tóm tắt phần ngữ pháp 82 English for electrical and electronic engineering Unit 1 CONDUCTORS INSULATORS AND SEMICONDUCTORS I. Reading and comprehension If we connect a battery across a body there is a movement of free electrons towards the positive end. This movement of electrons is an electric current. All materials can be classified into three groups according to how readily they permit an electric current to flow. These are conductors insulators and semiconductors. In the first category are substances which provide an easy path for an electric current. All metals are conductors however some metals do not conduct well. Manganin for example is a poor conductor. Copper is a good conductor therefore it is widely used for cables. A non-metal which conducts well is carbon. Salt water is an example of a liquid conductor. A material which does not easily release electrons is called an insulator. Rubber nylon porcelain and air are all insulator. There are no perfect insulators. All insulators will allow some flows of electrons however this can usually be ignored because the flow they permit is so small. see Fig Crosssection of copper wire mobile electrons An external influence Q repels a nearby electron The electron s neighbors find it repulsive if it moves toward them they move away creating a that h of i me radio ns which propagates through the material at the speed of light Semiconductor are mid-way between conductors and insulators. Under certain conditions they allow a current to flow .