Page 85 - Innovator's Science-8

iii. When the nega vely charged water droplets at the bo om of a cloud get close to the ground, things
on the ground like trees and buildings become posi vely charged. Normally, air stops these opposite
charges from mee ng because it acts like an insulator. But if the charges build up too much, the
insula ng air breaks down, and charges suddenly rush toward each other. This creates a bright flash
of light called lightning. Lightning can happen inside a cloud, between clouds, or between a cloud and
the ground. The lightning heats the air quickly, making it expand fast. This expansion creates the loud
sound we call thunder. A storm with both lightning and thunder is called a thunderstorm.
5. Explain the process that causes lightning.
Ans. When a storm forms, warm air rises high into the sky, where the air is colder. There, water droplets turn
into ice par cles. Strong winds move up and down, making the water droplets and ice par cles rub
against each other. This rubbing creates electric charges inside the cloud—the ice par cles become
posi vely charged and move to the top, while the water droplets become nega vely charged and stay at
the bo om.
As the nega vely charged bo om of the cloud comes close to the ground, the ground and objects like
trees and buildings become posi vely charged. Normally, air stops opposite charges from mee ng, but
when the charge difference becomes very large, the air can no longer block it. Then, the charges
suddenly flow toward each other, causing a bright flash of light called ligh ng. The lightning heats the air
around it very quickly, making it expand fast and crea ng a loud sound known as thunder.

6. Explain why holes are made in banners and hoardings.
Ans. Holes in banners and hoardings help prevent them from being blown away by strong winds. When wind
blows very fast, it creates areas of low pressure around the banner. If there are no holes, the wind hits
the surface directly, and the difference between high pressure in front and low pressure behind can
make the banner tear or fly away.
When holes are present, some of the wind passes through them, reducing the pressure difference on
both sides. This helps keep the banner or hoarding in place even in high-speed winds.

Put on your
Thinking cap Problem Solving Skills

A. Darken the correct options in the OMR Sheet: OMR Sheet
1. The moving air is called :

a. wind b. storm
c. cyclone d. all of these
2. __________ layer lies in the central zone of stratosphere. Wrong Methods
a. Oxygen b. Ozone Correct Method

c. Nitrogen d. All of these
3. With an increase in __________ , both density and pressure decreases 1. a b c d
rapidly.
a. al tude b. la tude 2. a b c d

c. depth d. none of these
4. Tropical cyclones that originate in __________ sea are known as typhoons. 3. a b c d
a. China b. Indian
4. a b c d
c. Japan d. All of these

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Science-8