Resistors

B) Cover the left column and translate the Russian words back into English.

capacity [ka'paesiti] емкость

power ['раиэ] мощность

heat теплота, нагрев

rate скорость, степень

to produce [pra'djuis] производить

- 16-

to change [tjemd3] менять(ся)

to vary [Vean] варьировать(ся)

low [lou] низкий

high [hai] высокий

fixed [fikst] постоянный

any (зд.) любой

variable [VEanabl] переменный

the (more)... the (more) чем (больше)... тем (больше)

2. Read the words and put down their Russian equivalents:

['tempratja] temperature _________________________________

['enac^i] energy

[wot] watt ________________________________

['konstant] constant __________________________________

[pou'tenjol] potential _________________________________

3. Translate into Russian using чем... тем:

1. The more one studies nature, the better one knows its laws.

2. The longer one learns, the more one knows.

3. The higher the atmosphere, the less is its pressure.

4. The heavier the object, the more work one has to do in order to lift it.

5. The greater the number of free electrons in any metal, the higher is its conductivity.

4. Translate into Russian. Mind no.

1. There is no energy in this machine.

2. No charges move through an open circuit.

3. No material is a perfect conductor of electricity.

4. No electric machinery is used without protection.

5. No special material is needed in this case.

A resistor is one of the most common elements of any circuit. Re­sistors are used:

1. to reduce the value of current in the circuit;

2. to produce IR voltage drop and in this way to change the value of the voltage.

When current is passing through a resistor its temperature rises high. The higher the value of current the higher is fr» tpmppratuiv» pf a rgfii?-

БИБЛИОТЕКА

1796 - Л -

Белгородского гос-го

технологического ун-та

им. В.Г. Шухова

tor. Each resistor has a maximum temperature to which it may be heated without a trouble. If the temperature rises higher the resistor gets open and opens the circuit.

Resistors are rated in watts. The watt is the rate at which electric en­ergy is supplied when a current of one ampere is passing at a potential difference of one volt. A resistor is rated as a 1-W resistor if its resis­tance equals 1,000,000 ohms and its current-carrying capacity equals 1/1,000,000 amp, since P = E x I = IR x I = I²R where P - power is given in watts, R - resistance is given in ohms and I - current is given in amperes.

If a resistor has a resistance of only 2 ohms but its current-carrying capacity equals 2,000 amp, it is rated as a 8,000,000-W resistor.

Some resistors have a constant value - these are fixed resistors, the value of other resistors may be varied - these are variable resistors.

5. Complete the sentences using the correct variant:

1. A resistor is used a) to measure the resistance.

b) to reduce the current.

c) to change the resistance.

d) to produce IR voltage drop.

b) its temperature rises. a) in ohms. b) in volts. c) in watts.   a) in amperes. b) in watts.   a) a constant value. b) a variable value.

2. When current passes through a re- a) its temperature drops, sistor

3. Resistors are rated

4. Power is given

5. Fixed resistors have

8. The higher the value of current, a) the lower is the temperature

of a resistor, b) the higher is the temperature of a resistor.

6. Complete the sentences using while. Follow the model on page 13.

1. The value of a fixed resistor is constant.................

2. Current-carrying capacity is given in amperes......................

3. The lower the value of current, the lower is the temperature of a resis­tor

4. An electric source produces energy.....................

7. Pair work. Put these questions to your groupmate and let him/her an­
swer them.

1. What is a resistor used for?

2. When does the temperature of a resistor rise?

3. What element is used to change the value of voltage?

4. How are resistors rated?

5. What types of resistors do you know?

6. When does a resistor get open?

7. What does an open resistor result in?

8. What is the difference between a fixed resistor and a variable resistor?

9. How much is the current-carrying capacity of a two-ohm resistor? 10. What resistors have a variable value?

8. Solve the problem:

What is the maximum current for a resistor having a 5-watt capacity and a resistance of 20,000 ohms?

9. Pair work. Think of three similar problems of your own. Ask your
groupmate to solve them.

6. The value of a variable resistor

7. A two-ohm resistor rated as a 8,000,000-W resistor

a) is fixed.

b) is varied.

a) has a current-carrying capac­ity equal to 2,000 amp.

b) has a current-carrying capac­ity equal to 200 amp.

i. a) Cover the right column and read the English words. Translate them into Russian and check your translation.

b) Cover the left column and translate the Russian words back into English.

cell [sel] элемент

output ['autput] емкость, мощность

-18

2*

- 19-

bulb [Ьл1Ь] электрическая лампа

to light [lait] зажигать, освещать

to increase [in'kri:s] увеличивать(ся), возрастать

to substitute заменять

... and so on и так далее

2. Read the words and put down their Russian equivalents:

[ilektroud] electrode

ji'lektralait] electrolyte

[sta:t] to start

j'opareit] to operate

['aisaleit]

to isolate

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