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Prof. Dr.Sc.Techn. Eng. Stefan Iliev, ROSTI Ltd. Bulgaria
The threat of striking lightning is greater for Bulgarians, than elsewhere. Bulgaria is a region with powerful lightning activity. This is why lightning frequently strikes cattle and people, and the fires caused by them lead to considerable losses.
WHAT IS LIGHTNING
Opposite electric charges are created through induction between clouds and objects on earth. Owing to electrical conductivity of the air and the medium between them an electric arc - lightning - arises, accompanied with a sound - thunder.
Metal objects. Wet trees, the bodies of live creatures attract lightning. The passing of lightning current prefers vertically situated objects with a horizontal orientation, such as for example, fences, thus expanding the range of damage.
Michael Faradey (1791-1867), the English physicist and chemist has proven that in a metal cage the external electromagnetic field, including lightning, did not provoke a devastating effect.
Another fact is that the interval between the lightning and thunder indicates the proximity of the lightning. An interval of 1 second corresponds to about 330 m the place where the lightning struck.
WHEN WE ARE TRAVELING
When we are traveling in a car, bus, truck or tractor, the metal body functions as a cage of Faradey and protects the passengers from lightning. Nevertheless the driver may take fright and lose control over the vehicle.
Experience has shown that when there is lightning there may be a threat for the wheels of the car. Rubber is a good insulator, however they could be damaged by the heat of the current from the lightning.
This is why it is recommended that drivers who find themselves in a strong storm to do the following:
The lightning might have affected traffic lights, street lights, or warning signalization at level crossings, pylons or trees may have been knocked down.
It is best for cyclists to seek shelter in a house, in some vehicle, under a steel bridge or a concrete bridge, keeping away from the bicycle.
If this is not possible get off the bicycle or motorbike, get away several meters from them and kneel in some hollow.
There have been cases of lightning striking planes in the air or on the ground. Usually there are no consequences. Once again here we have the effect of Faradey's cage. No doubt lightning can damage some electronic instruments on board and affect flying control.
WHEN THERE IS A STORM IN THE FIELDS
There are two risks:
The current which passes through the human body can cause burns, temporary paralysis or death.
The threat is smaller is one kneels in a hollow, with the hands around the legs, the feet one over the other. In this way 'foot tension' is lowest.
By no means should one lie on the ground.
Cattle, horses and other quadrupeds are much more threatened by indirect lightning than humans as the difference in the tension between the front legs and the hind legs is considerably greater.
This is why one should get off the horse he is riding.
DANGEROUS PLACES DURING A STORM ARE THE FOLLOWING:
A storm is a real threat if the time between lightning and the thunder is less than 10 sec. Then one should take shelter:
If a storms sets in by surprise and it is not possible to find shelter, when the time between the lightning and the thunder is less than 5 sec, all we can do is to kneel to the earth.
If there is a group the distance between everyone in the group should be 3-5 meters.
IT IS WRONG TO DO THE FOLLOWING:
WHEN HAVING A BATH IN THE BATHROOM
When a lightning strikes it is possible that a minimal part of the current may pass through the metal pipes of the water supply system.
In spite of that there is no risk, when touching the water tap or below the shower, if the water supply system in the building is earthed according to technical requirements.
STORMS AT CAMPING SITES
The risk of lightening at camping sites is reduced if the camping site is suitably chosen.
This can be done with the application of small and simple protective measures:
SUNSHADES AND UMBRELLAS ARE DANGEROUS
As they strongly attract direct lightning. When a storm breaks out both sunshades and other sharp objects should be left on the ground. Lakes and rivers are more dangerous than the sea. Marine water has more salt and less electrical resistance.
If someone has been struck by lightning his heart may stop. In such cases artificial respiration should be undertaken and a massage of the heart.