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Understand Lightning
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- Meaning: It is an electric spark caused by charge imbalance between clouds and the ground, due to accumulation of charge in the cloud.
- In ancient times, people feared it, thinking it was the wrath of gods.
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Lightning: Historical Insights and Scientific Milestones
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- Discovery: In 600 BC, the Greeks discovered the phenomenon of static electricity, noticing that amber, when rubbed with fur, attracted light objects due to electric charges.
- Realization: In 1752, Benjamin Franklin scientifically proved the correlation between lightning and sparks from clothing, a realization that took the world 2000 years to acknowledge.
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Static Electricity: Charging and Electron Transfer in Lightning
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- Static Electricity: When objects are rubbed together, the movement of electrons occurs, resulting in the positive charging of one object and the negative charging of the other, a fundamental phenomenon in static electricity.
- Transfer of Charges: The rubbing of a plastic refill with polythene results in charge transfer, leading to the formation of charged objects.
- Examples: This phenomenon can be observed in various materials, including balloons, erasers, and steel spoons.
- Electric charges produced by rubbing remain static until they are set in motion, forming an electric current.
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Electric Charges and Their Interaction in Lightning
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- Movement of Electrons: During the rubbing process, electrons move from one object to another, causing an excess of electrons in one and a deficiency in the other, resulting in the creation of charged objects.
- Example: When a glass rod is rubbed with silk cloth, the glass becomes positively charged, and the silk cloth becomes negatively charged, showcasing the transfer of electric charges between them.
- Negatively Charged: Objects having an excess of electrons are called negatively charged.
- Positively Charged: Objects having a shortage of electrons are called positively charged.
- Electric Current: The electrical charges generated by rubbing are static. They do not move by themselves. When charges move, they constitute an electric current.
- The current in a circuit which makes a bulb glow, or the current that makes a wire hot, is nothing but a motion of charges.
- Like charges repel each other. Unlike charges attract each other.
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Earthing in Lightning Protection
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- When we touch charged aluminum foil, charges flow through our bodies since humans are good conductors, grounding the charges to the earth.
- Earthing: The process of transferring charges from a charged object to the earth is called earthing.
- Earthing is provided in buildings to protect us from electrical shocks due to any leakage of electrical current.
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Occurrence of Lightning
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- In rain or thunderstorms, air rises while water droplets fall.
- During rain, charges segregate, positive charges accumulate near the upper edges of clouds, and negative charges accumulate near the lower edges.
- Additionally, positive charges accumulate on the ground.
- Between the clouds and the ground, the air is present which typically exhibits poor conductivity for charges.
- However, when its resistance diminishes, it begins to conduct charges.
- Negative and positive charges collide, resulting in bright light and sound, visible to us as lightning, known as electric discharge.
- Electric discharge can happen between clouds and the earth’s surface or between two clouds in the atmosphere.
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Lightning Safety Guidelines to Follow
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Outdoors:
- Seek refuge in a secure location, like a small grove of trees.
- If you are inside a vehicle, remain inside with closed doors and windows.
- Keep a safe distance from metal poles.
- Avoid lying on the ground; instead, crouch down with your head protected by your hands.
Indoors:
- Refrain from touching telephone and electrical wires.
- Avoid taking a bath during a thunderstorm.
- Unplug electrical appliances as a precautionary measure.
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Lightning Conductors
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- This conductor is a device used to protect buildings from lightning.
- In the construction phase, a metallic rod is meticulously placed along the building’s upper edge.
- One end extends into the air, creating a lightning-attracting point, while the other end is firmly grounded below the surface, ensuring a secure path for the discharge.
- When a thunderstorm strikes the rod, charges transfer to the earth, leaving the building unharmed and protected.
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