Lightning is a killer !

Lightning, a natural disaster and a frequent killer is something most of us are afraid of. Some of you may have had frightful experiences with lightning.

Lightning is a natural phenomenon which cannot be stopped, but the harmful effects could be minimised.

It is a fact that damage to property and loss of life due to lightning is on the increase in Sri Lanka and in other countries too today. Here are some valuable facts about lightning for your knowledge bank and some precautionary measures you could take to stay safe.

* Lightning activity over Sri Lanka is on a peak during the two inter-monsoon seasons of March-April and October-November.

* Well developed convective clouds (read about the different types of clouds) which produce thunderstorms are technically known as ‘Cumulonimbus’.

*A well developed cumulonimbus cloud is electrically charged.

* Lightning therefore is merely electrical discharges associated with the charged cumulonimbus clouds.

*These electrical discharges are grouped into three main types, depending on the way of discharging.

They are:

(a) Ground flash or cloud to ground flash which is a discharge between clouds and the earth.

(b) Cloud flash or intra cloud flash which is a discharge within a cloud.

(c) Air flash which is a discharge between clouds and the atmosphere.

* The electric current of a ground lightning flash is about 25,000 Amperes (25,000 A). The potential difference between charged cloud and the earth is about 1000 million volts.

* A lightning flash, after travelling about half a kilometre from a cloud, seeks a conducting path to naturalise itself. It is attracted to:

Tall buildings in developed areas

Tall trees in a natural environment

* Conducting (metal) structures, communication towers, telephone and power supply lines and TV antennas attract closeby lightning flashes.

* Once a flash of lightning strikes a building it will pass through the conductive materials of the building such as the reinforcing steel in concrete columns and slabs, wiring, electrical circuits and metal structures, if no safe way is provided for the lightning to travel down to the earth.

* A part or the whole current of a lightning flash which has hit a closeby TV antenna, power line or telephone may travel to a building via the electrical (metal) connection between the point of strike and the building.

* There are many different ways by which lightning could impact people and properly.

They are:

(a) Direct hit - This occurs when a lightning flash coming down from a cloud hits an object (man, animal or something else) directly.

(b) Contact potential - Experiencing shock when there is contact with something that acts as a conductor such as a tree, building or lightning conducting wire.

(c) Side flash - Experiencing shock when standing close to a building, tree or conducting wire that acts as a past of a conductor of a lightning current.

(d) Step voltage - Voltage differences between feet resulted by a current spreading from a point of lightning strike on the ground.

* As electric power supply cables, telephone cables and TV antenna cables are good lightning conductors, during a thunderstorm always keep:

(a) All electrical instruments disconnected from the main power supply.

(b) Ideally, television antennas should be connected to an earthed conductor.

If no such provision has been made disconnect the TV and place the antenna socket close to the earth, outside the house, where it is not likely to be trampled by any person or animal, accidentally.

(c) Avoid touching or standing close to metal structures (especially in construction sites) metal clothes lines or wire fences.

(d) Avoid handling electrical equipment such as electrical irons, the TV, radio, and also the telephone, not just landlines, but also mobiles.

(e) Do not work in open fields using metal instruments like mammoties or iron rods.

(f) Do not dabble with water, especially outdoors and also avoid standing under tall trees. Find shelter as soon as possible. If you have no choice, but to stay in an open area, stay low and avoid being the tallest object in the area.

* In the instance, the interval between a lightning flash and the sound of thunder is less than 15 seconds, take precautionary measures quickly.

This means the danger of a lightning strike is immediate.

Even though lightning is dangerous and many lives have been lost and property destroyed as a result of it, it is something that should occur. This is because lightning helps maintain the electrical balance of the Earth.

There are many proposals to harness the energy of a lightning flash, but apart from it being a difficult task, there is also concern as to how profitable it is, simply because it would definitely affect the natural electrical balance of the globe. We are yet to know what such an imbalance would lead to.

So, all we can do is take precautionary measures as lightning simply cannot be controlled.

Facts: Courtesy Department of Meteorology.

Pic: Internet