Lightning is simply a natural electrical discharge of very short duration and high voltage between a cloud and the ground or between a cloud and another cloud or within a cloud. It is usually accompanied by a bright flash and thunder. For cloud to ground lightning, it means that the cloud is one terminal of the circuit and the ground is the other terminal.
A lightning strike delivers about 300kV of electric shock! The temperature of the lightning itself is close to 30,000oC! This is why lightning sometimes sets building on fire.
Thunder however, is the sound caused by lightning. The sound is as a result of the sudden expansion of air around a lightning bolt, caused by increase in pressure and temperature from the lightning.
Lightning and thunder actually happen at the same time. However, the speed of light is approximately 300,000,000 m/s while the speed of sound in air is around 340 m/s. As a result, we see lightning first before we hear the sound of thunder when lightning strikes.
For the formation of lightning, thunderclouds must be present. When clouds build up in the sky, at the tops of the clouds, temperature is below freezing point and the water vapour turns into ice there. So, the clouds become a thunderclouds.
In a thundercloud, lots of small bits of ice bump into each other as they move around. All these collisions cause a build up of electrical charges. Eventually, the whole cloud is filled up with electrical charges. Lighter and positively charged particles are formed in the top of the cloud while heavier and negatively charged particles sink to the bottom of the cloud.
When the positive and negative charges in the cloud grow large enough, a giant spark – lightning – occurs between the two charges within the cloud. This is like a static electricity sparks you see, but much bigger. This is the formation of within cloud lightning.
For the formation of cloud to ground lightning, it happens this way:
Already, the negative charges in the cloud are built up in the bottom of the cloud. On the surface of the Earth, there would be a build up of positive charges beneath the cloud. Like charges repel; unlike charges attract. The ground’s positive charges concentrate around anything that sticks up e. g. trees, lightning conductors, tall buildings, even people! The negative charges under the cloud and the positive charges on the ground attract one another. As the charges continue to build up, the positive charges from the ground connect with the negative charges from the cloud. This results in a spark of lightning strikes. (www.planet-science.com)
When a bolt of lightning strikes part of a human, some of the bad things that happen include:
- passage of 300kV of electrical shock through the person
- a certain degree of burns
- bursting blood vessels
- shredding of clothing
- forceful removal of shoes
- cardiac arrest
- damage to the cardiac muscles/heart attack
- loss of conscioussness
- brain damage (lightning current cooks the structure of the brain)
- temporary or permanent paralysis
- deafness (due to damage to ear drum)
We need to take necessary safety measures for our safety during a stormy weather. Some of the safety measures include:
- Seek shelter in a building or a car
- Avoid isolated trees
- Get off bicycles, motorcycles or horses
- If you can’t get a safe place to hide, then, sit or lie down. If you have to move, then crawl.
- Avoid holding metal
- Wait for about 30 minutes after thunder before returning to open areas
- For another day, check whether forecast before going out
You can watch the video below for more:
(Video Credit: Vocalbug Communications Pvt, Photo Credits: wallpapers-xs.blogspot.com, vimalthiagarajan.wordpress.com, hannahandphysics.blogspot.com, www.hko.gov.hk)