Text 11. Electric shock. Safety electric system.

1. Прочтите и переведите.

Vocabulary:

strength – сила

dangerous – опасный

shock – шок, удар

lethal – смертельный

to deenergize – лишать энергии

attending personnel – обслуживающий персонал

to decrease – уменьшать(ся)

to increase –усиливать(ся)

to take into consideration – принимать во внимание

installation – установка

to check – проверять

to detect – открывать, обнаруживать

to eliminate – устранять

faulty – ошибочный, неисправный

The strength of current depends on both the voltage and on the resistance in a circuit. A current of 5 ohm is dangerous for a man; it may result in an electric shock. One gets an electric shock in case one touches live conductors when the power is on. And a current of 10 ohm and higher is lethal. Thus, before working on a circuit, deenergize it and work on it with the power off.

Earthing system serves to protect attending personnel from electric shock when voltage appears on parts that are normally dead. The risk of an electric shock decreases with decreasing voltage. In wet and hot atmosphere the risk of electric shock increases. Safe voltage for circuits used in dry atmosphere is under 36V. When the power is on contacts with live conductors are dangerous for life. When a live conductor is touched with both hands the resistance of the conductor is from 10,000 to 50,000 ohm. When a live conductor is touched with one hand he resistance is much higher. The higher is the body resistance, the smaller is the current that flows through the body. Take it into consideration and work with one hand if the power is on. Or work on the circuit with the power off!

Thus measure is taken to protect attending personnel from contact with live parts of installation under voltage.

The danger of electric shock disappears provided the metal parts of installation under voltage are connected with ground by means of safety earthing. Connecting to ground is made by means of measuring devices. The faulty parts should be detected, eliminated, and replaced by new ones.

2. Ответьте на вопросы по тексту:

1. What does the strength of current depend on?

2. What does electric shock result from?

3. What parts are termed dead (live)?

4. In what case does the risk of electric shock decrease (increase)?

5. When is the resistance of a live conductor much higher?

6. When does the danger of electric shock disappear?

3. Переведите следующие словосочетания:

Power decrease, dry air, hot atmosphere, dead conductor, live conductors, power on position, power off position, safety earthing system, dangerous decrease of voltage, live contact.

4. Выберите правильное слово:

1. The danger of electric shock … (appears, disappears) when the conductor becomes … (live, dead).

2. Current passes through faulty … (earthed, unearthed) parts of installations when the power is on.

3. Low accuracy of measurement is … (an advantage, a disadvantage) of the measuring device.

4. The danger of electric shock … (increases, decreases) in the wet and hot atmosphere.

5. No current flows through a … (dead, live) conductor.

5. Выберите правильный вариант:

1. Earthing system serves …

1. as protection from electric shock b) as connection with ground

2. Voltage appears on …

1. dead parts b) live parts

3. Contact with live conductors is …

a) dangerous b) safe

4. Connection to ground is made …

1. by means of wire conductors b) by means of earthing electrodes

5. Danger of electric shock disappears if the frame …

a) is earthed b) is unearthed