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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 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 1.1)
Fig.1.1:
Semiconductor are mid-way between conductors and insulators. Under certain
conditions they allow a current to flow easily but under others they behave as
insulators. Germanium and silicon are semiconductors. These are known as
thermistors. The resistance of thermistors falls rapidly as their temperature
rises. They are therefore used in temperature sensing devices.
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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 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 1.1)
Fig.1.1:
Semiconductor are mid-way between conductors and insulators. Under certain
conditions they allow a current to flow easily but under others they behave as
insulators. Germanium and silicon are semiconductors. These are known as
thermistors. The resistance of thermistors falls rapidly as their temperature
rises. They are therefore used in temperature sensing devices.
Do Drive thay đổi chính sách, nên một số link cũ yêu cầu duyệt download. các bạn chỉ cần làm theo hướng dẫn.
Password giải nén nếu cần: ket-noi.com | Bấm trực tiếp vào Link để tải:
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