Electricity

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John: And what is thunder?
Mr. Robertson: Thunder comes because the electricity tears its way through the air.
Task7. Read the text Safety Earthing System. Electric Shock and answer the following questions.
Safety Earthing System. Electric Shock.
The strength of current depends on both the voltage and the resistance in a circuit. A current of 50 mA is dangerous for a man and a current of 100 mA and higher is lethal. Earthing system serves to protect attending personnel from electric shocks 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 36 V. When the power is on, contacts with live conductors are dangerous for life. Thus, measures are taken to protect attending personnel from contacts with live parts of installations under voltage.
The danger of an electric shock disappears provided the metal parts of installations under voltage are connected with ground by means of safety earthing.
Connecting to ground is made by means of earthing electrodes which are connected directly with ground.
The insulation resistance of any installation should be regularly controlled by means of measuring devices. The faulty parts should be detected, eliminated, and replaced by new ones.
1. What does an earthing system serve for?
2. What parts are termed dead (live)?
3. In what air does the risk of an electric shock decrease?
4. By what means is connection to ground made?
5. What does an electric shock result from?
6. Is a current of 50 mA dangerous for a man?
7. Is wet and hot atmosphere dangerous for the attending perso