2015-08-21
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For example: The operation of a vacuum diode is described in the text.
SPECIALIST READING
Mark the following sentences as true (T) or false (F). Then read the text “Diodes” and check yourself.
1. Electronics is the study of conduction of electricity.
2. In some vacuum tubes current flows through a gas.
3. A diode has a cathode with a heater and a plate.
4. The cathode emits electrons.
5. Negative voltage on the plate repels electrons.
6. If a positive voltage is applied current does not flow.
7. A diode permits current to flow in only one direction.
8. Diodes are used as rectifiers of alternating voltages, as detectors of radio signals, as switching devices, etc.
We can define electronics as the study of conduction of electricity in a vacuum, in gases and in semiconductors. The conduction of electricity in a vacuum, for example, occurs in vacuum tubes. Though in some vacuum tubes current flows from one element to the other through a gas.
Every vacuum tube diode has a cathode with a heater and a plate. When the circuit is completed the cathode emits electrons. Negative voltage on the cathode repels the electrons. Positive voltage on the plate attracts the electrons. The current flows through the tube. If a negative voltage is applied to the plate current does not flow. Thus a diode permits current to flow in only one direction.
A semiconductor diode also conducts current in one direction, but the physical principles, which permit it to do this are different. Diodes are used as rectifiers of alternating voltages, as detectors of radio signals, as switching devices.
Read the text again and complete the sentences with the correct ending.
1. Electronics is …
2. The conduction of electricity in a vacuum …
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3. In some vacuum tubes current …
4. Every vacuum tube diode …
5. When the circuit is completed …
6. Negative voltage on the cathode …
7. Positive voltage on the plate …
8. If a negative voltage is applied to the plate…
9. A diode permits current to …
10. Diodes are used as …
Work in pairs. Ask your partner questions based on the text. Make sure you use correct auxiliary verb.
For example: Define electronics (How) - How can we define electronics?
1. The conduction in a vacuum occurs (Where) – …
2. Every vacuum diode has (What) – …
3. The cathode emits (What) – …
4. Negative voltage (Where) – …
5. … attract the electrons (What?) – …
6. The current flows through the tube (When?) – …
7. Current does not flow (Under what conditions?) – …
8. … to flow in only one direction (What?) – …
9. Diodes are used as (Where?) – …
