TASK 2. Read the text and translate it from English into Russian. RESISTORS
Now any circuit consists essentially of a combination of resistance, inductance and capacitance with one or more sources of electromotive force. Let us consider these main components of a circuit. At first let us speak about resistance and resistors.
The property of “opposing” or weakening the current is called electrical resistance. Georg Ohm in the early part of the 19th century performed a series of experiments which established the law connecting voltage and current. Symbolically, Ohm’s law is often written: R = V/I. Resistance equals voltage divided by current. The unit of resistance is the Ohm. An ohmmeter is used to measure the value of resistance in a circuit. Different materials have different resistances. All substances may be divided into three groups according to their resistivities: conductors, semiconductors and dielectrics or insulators. A good conductor is a material of low resistivity. An insulator is a material of very high resistivity.
The resistance of a conductor depends on the length, the cross sectional area, the material of the conductor and its temperature. A resistor is a device employed to limit the value of current. Resistors may be fixed or variable. Fixed resistors have a constant value. The value of variable or adjustable resistors may be varied. A rheostat is another type of a variable resistor.
TASK 3. Answer the following questions and retell the text. 1. What main components does a circuit consist of? 2. What’s electrical resistance? 3. What is the unit of resistance? 4. Is an ohmmeter used to measure the value of resistance? 5. Into what groups may all substances be divided according to their resistivities? 6. What substance is called a good conductor? 7. What does the resistance of a conductor depend on? 8. Have insulators a very low or high resistance? 9. What two types of resistors do you know?
TASK 4. Read the words and pay attention to the suffixes used. to resist – resistance – resistor; to insulate – insulator; to conduct – conductor – conduction; to depend – dependence; to discover – discovery; to produce – production; to equal – equality; to consider – consideration; to measure – measurement; to improve – improvement; to invent – inventor – invention.
TASK 5. Match the words. 1. substance a) chief
2. main b) to change
3. to use c) to regulate
4. fixed d) to produce
5. to make e) stable
6. to adjust f) material
7. to vary g) to employ
TASK 6. Fill in the gaps and translate the sentences. 1. Current passes through . . . with great difficulty. a) conductors; b) insulators; c) metals. 2. Fixed resistors have a . . . value. a) varied; b) constant; c) changeable. 3. The value of a . . . is varied. a) variable resistor; b) fixed resistor; c) very stable resistor (высокостабильное сопротивление) 4. Current equals . . . divided bу resistance. a) resistivity; b) inductance; c) voltage. 5. A . . . which is a good insulator at low temperature may be a good conductor at high temperatures. a) property; b) substance; c) source. 6. An ohmmeter is used to . . . the value of resistance in a circuit. a) divide; b) measure; c) transmit. 7. An engineer must know physical and mechanical . . . of materials. a) components; b) achievements; c) properties. 8. Mendeleyev discovered the periodic. . . . a) application; b) unit; c) law.
TASK 7. Fill in the gaps with the verbs in brackets, use the Active Voice. 1. A rheostat … (to be) a resistor whose resistance value may be varied. 2. Last week they … (to make) many experiments. 3. Any circuit … (to consist of) a combination of resistance, inductance and capacitance. 4. Next week he … (to demonstrate) this new device. 5. Popov … (to invent) the first radio-set. 6. A resistor … (to be) a device to limit the value of current. 7. An ohmmeter … (to measure) the value of resistance in a circuit. 8. Resistance … (to equal) voltage divided by current.
TASK 8. Fill in the gaps with the verbs in brackets, use Participle II. 1. The work … (to do) by these scientists resulted in many new discoveries. 2. A new transmitting station … (to build) in our region is very powerful. 3. The phenomenon … (to study) by this engineer is of great importance for our work. 4. Radio waves … (to radiate) by the antenna travel in all directions. 5. The experiments … (to make) by him were very useful for our work. 6. New measuring instruments … (to develop) in this laboratory will be used in this experiment. 7. A device … (to employ) to limit the value of current is a resistor. 8. The antenna receives only a small part of energy … (to radiate) by the transmitter.
TASK 9. Listen to the recording and fill in the gaps.
