SOME NATURAL PHENOMENA 5
CHAPTER
CONTENTS TYPES OF CHARGES AND
Charging by Rubbing
THEIR INTERACTION
Types of charges and their There are two kinds of charges same kind of charges
interaction repel each other, while charges of different kind attract
Transfer of charge & earthing each other
Rain It is a convention to call the charge acquired by a glass
Lightning rod when it is rubbed with silk as positive. The other
kind of charge is said to be negative.
Lightning safety
Lightning conductors TRANSFER OF CHARGE & EARTHING
Earthquakes
Take an empty jam bottle. Take a piece of cardboard
Causes of Earthquakes
slightly bigger in size than the mouth of the bottle.
Protection against Earthquakes
Pierce a hole in it so that a metal paper clip could be
Seismograph inserted. Cut two strips of aluminium foils. Hang them
on the paper clip as shown. Insert the paper clip in the
cardboard lid so that it is perpendicular to it (Fig.).
CHARGING BY RUBBING Charge a refill and touch it with the end of the paper
clip. Observe that they repel each other.
The ancient Greeks knew as early as 600 B.C. that
when amber (amber is a kind of resin) was rubbed
with fur, it attracted light objects such as hair. If
you take off these clothes in the dark, you see even
a spark and hear crackling sound.
In 1752 Benjamin Franklin, an American scientist,
showed that lightning and the spark from your
clothes are essentially the same phenomena.
When a plastic comb is rubbed with dry hair, it
acquires a small charge. These objects are called
charged objects. In the process of charging the
plastic comb, hair also get charged.
The method of charging by friction is called
Fig. : A simple electroscope
frictional charging.
, This device is known as electroscope. Thus, we find
that electrical charge can be transferred from a charged
object to another through a metal conductor.
Touch the end of the paper clip gently with hand and
you will find a change in the foil strips. They come back
to their original state. The reason is that the foil strips
lose charge to the earth through your body. We say that
the foil strips are discharged. The process of
transferring of charge from a charged object to the earth
is called earthing.
Fig. : Accumulation of charges leading to lightning
RAIN LIGHTNING SAFETY
Water from the water bodies on the surface of the earth Finding a safe place :
get converted into water vapour by evaporation goes
A house or a building is a safe place. If you are
into the atmosphere and then rises up in the air. The
travelling by car or by bus, you are safe inside with
water droplets, which float in the air in the form of
windows and doors of the vehicle shut.
clouds. These water droplets by colliding against each
other and stick together to form bigger water droplets. If outside the home :
When these water droplets become too heavy to float, Open vehicles, like motorbikes, tractors,
they come down as rain. construction machinery, open cars are not safe.
Open fields, tall trees, shelters in parks, elevated
places do not protect us from lightning strokes.
LIGHTNING
Carrying umbrella is not a good idea at all during
thunderstorms.
During the development of a thunderstorm, the air
If you are in a forest, take shelter under shorter
currents move upward while the water droplets move trees. If no shelter is available and you are in an
downward. These vigorous movements cause separation open field, stay far away from all trees. Stay away
of charges. The positive charges collect near the upper from poles or other metal objects. Do not lie on the
ground. Instead, squat low on the ground. Place your
edges of the clouds and the negative charges accumulate hands on your knees with your head between the
near the lower edges. There is accumulation of positive hands (Fig.).
charges near the ground also.
When the magnitude of the accumulated charges
becomes very large, the air which is normally a poor
conductor of electricity, is no longer able to resist their
flow. Negative and positive charges meet, producing
streaks of bright light and sound. We see streaks as
lightning (Fig.). The process is called an electric
discharge. The process of electric discharge can occur
between two or more clouds, or between clouds and the
earth & at that moment air near lightning path reaches
up to 30,000°C Fig. : Safe position during lightning
This position will make you the smallest target to
be struck.
CHAPTER
CONTENTS TYPES OF CHARGES AND
Charging by Rubbing
THEIR INTERACTION
Types of charges and their There are two kinds of charges same kind of charges
interaction repel each other, while charges of different kind attract
Transfer of charge & earthing each other
Rain It is a convention to call the charge acquired by a glass
Lightning rod when it is rubbed with silk as positive. The other
kind of charge is said to be negative.
Lightning safety
Lightning conductors TRANSFER OF CHARGE & EARTHING
Earthquakes
Take an empty jam bottle. Take a piece of cardboard
Causes of Earthquakes
slightly bigger in size than the mouth of the bottle.
Protection against Earthquakes
Pierce a hole in it so that a metal paper clip could be
Seismograph inserted. Cut two strips of aluminium foils. Hang them
on the paper clip as shown. Insert the paper clip in the
cardboard lid so that it is perpendicular to it (Fig.).
CHARGING BY RUBBING Charge a refill and touch it with the end of the paper
clip. Observe that they repel each other.
The ancient Greeks knew as early as 600 B.C. that
when amber (amber is a kind of resin) was rubbed
with fur, it attracted light objects such as hair. If
you take off these clothes in the dark, you see even
a spark and hear crackling sound.
In 1752 Benjamin Franklin, an American scientist,
showed that lightning and the spark from your
clothes are essentially the same phenomena.
When a plastic comb is rubbed with dry hair, it
acquires a small charge. These objects are called
charged objects. In the process of charging the
plastic comb, hair also get charged.
The method of charging by friction is called
Fig. : A simple electroscope
frictional charging.
, This device is known as electroscope. Thus, we find
that electrical charge can be transferred from a charged
object to another through a metal conductor.
Touch the end of the paper clip gently with hand and
you will find a change in the foil strips. They come back
to their original state. The reason is that the foil strips
lose charge to the earth through your body. We say that
the foil strips are discharged. The process of
transferring of charge from a charged object to the earth
is called earthing.
Fig. : Accumulation of charges leading to lightning
RAIN LIGHTNING SAFETY
Water from the water bodies on the surface of the earth Finding a safe place :
get converted into water vapour by evaporation goes
A house or a building is a safe place. If you are
into the atmosphere and then rises up in the air. The
travelling by car or by bus, you are safe inside with
water droplets, which float in the air in the form of
windows and doors of the vehicle shut.
clouds. These water droplets by colliding against each
other and stick together to form bigger water droplets. If outside the home :
When these water droplets become too heavy to float, Open vehicles, like motorbikes, tractors,
they come down as rain. construction machinery, open cars are not safe.
Open fields, tall trees, shelters in parks, elevated
places do not protect us from lightning strokes.
LIGHTNING
Carrying umbrella is not a good idea at all during
thunderstorms.
During the development of a thunderstorm, the air
If you are in a forest, take shelter under shorter
currents move upward while the water droplets move trees. If no shelter is available and you are in an
downward. These vigorous movements cause separation open field, stay far away from all trees. Stay away
of charges. The positive charges collect near the upper from poles or other metal objects. Do not lie on the
ground. Instead, squat low on the ground. Place your
edges of the clouds and the negative charges accumulate hands on your knees with your head between the
near the lower edges. There is accumulation of positive hands (Fig.).
charges near the ground also.
When the magnitude of the accumulated charges
becomes very large, the air which is normally a poor
conductor of electricity, is no longer able to resist their
flow. Negative and positive charges meet, producing
streaks of bright light and sound. We see streaks as
lightning (Fig.). The process is called an electric
discharge. The process of electric discharge can occur
between two or more clouds, or between clouds and the
earth & at that moment air near lightning path reaches
up to 30,000°C Fig. : Safe position during lightning
This position will make you the smallest target to
be struck.
