some natural phenomenon, class 8 notes
Some natural phenomena
Phenomena: the process occurred in the environment / universe is called phenomena example lighting earthquake
Spark: when two wires of
different polarities touch together a small light appears this is known as a
spark example:
- when we plug the switch in the socket smaller spark will seen in socket
- . when we wear out woolen cloth small lightning with sound produce this is spark
- The spark is produced due to differences in charges of the bodies
Creation of charge:
Every object is made up of atoms. When a
object rubs over another object then due to heat energy electron get released
from first object and get deposited on other thus bodies become charged.
Positive charge bodies: the object
from which electron released and fall called positive charge bodies.
Negative charged bodies: the object
on which electron fall and settled down called negative charged bodies.
Convention
of Positive and Negative charges:
When we rub a scale on
and dry here it start attracting the small bits of paper
Glass rod is rubbed with the silk; the charge of glass rod is taken as positive while that of silk is taken as negative
Charges is transferred to other body when
- 1. Other body is neutral
- 2. other body with opposite charge when it transferred then opposite charged decreased
- 3. other body with the same charge but in less quantity
Interaction between like and unlike charges: Like
charges repel, while unlike charges attract.
Electroscope: It is a device
or an instrument that can be used to test whether an object is carrying a
charge or not.
1. When
the charged body touched to the metal disk, then charge is transferred and the
gold foil leaf separates.
2. If
another body is touched to the disk and the separation between disk increases,
it means the bodies have same charge as the previous body has.
3. If
another body is touched to the disk and the separation between disk decreases,
it means the bodies have opposite charge as the previous body has.
4. It
does not tell about the nature of charge a body have i.e. positive or negative.
Lightning:
Lightning
is caused by a compilation of charges in the clouds it is generally seen in
rainy seasons. Lightning is deadly so we
have to protect ourselves from it. In 1752
Benjamin and flanking (American scientist) show that lightning and sparks is
the same phenomena.
The process of an electric discharge between clouds
and the earth or between different clouds caused lighting the process of
lightning is explained below
- upward movement of air current and downward
movement of water droplet during the development of a thunderstorm cause
the separation of the charge
- positive charge collect near the upper
edge of the clouds and the negative accumulated near the lower edge,
positive charge accumulated near the ground also
- when
the magnitude of accumulated charge become very large the air which is
normally poor conductor of electricity is no longer able to resist and
positive charge meet producing streak of lights and sound
Electric Discharge
The process of flow of charge from cloud
to cloud or from cloud to earth due to the separation of positive and negative
charges is called an electric discharge.
Lightning safety
Outdoor
1. Do not take shelter
of metal shed and big trees
2. Do not touch metal
poles
3. If you are in car or
bus, stay inside it.
4. Stay away from water.
5. Crouch on the ground with your head down.
Indoor
1. Do not switch on the TV,
mobile, radio etc
2. Don't touch metal
pipe, taps.
3. Don't take a bath.
4. Don't sit near the
door and windows.
Earthing
The
process of transferring charges from a charged object to the earth is called
earthing.
Lightning
Conductors
- Lightning conductors help to
protect buildings during lightning.
- They consist of a metal rod
that is taller than the building which is installed within the walls
during construction. They run all the way to the earth and act as a direct
passage for electric discharge during lightning.
Earthquake :
Earthquake
it is a sudden shaking or trembling of earth which last for a very short time. We
are not able to predict earthquakes accurately. Earthquake occurs all the time
over the Earth.
Cause: earthquakes are caused by deep disturbance deep down inside the
uppermost and fragmented layer of the earth called crust. Each fragment of the
crust is called a tectonic plate.
Fault zones: The boundaries of the plates are the weak zones where
earthquakes are more likely to occur the weak zones are also known as false
zones. Kashmir western and central region, the whole of North East run of kuchh
are more threatened to be earthquake in India
|
magnitude level |
category |
effects |
|
less
than 1.0 to 2.9 |
micro |
generally
not felt by people, though recorded on local instruments |
|
3.0–3.9 |
minor |
felt
by many people; no damage |
|
4.0–4.9 |
light |
felt
by all; minor breakage of objects |
|
5.0–5.9 |
moderate |
some
damage to weak structures |
|
6.0–6.9 |
strong |
moderate
damage in populated areas |
|
7.0–7.9 |
major |
serious
damage over large areas; loss of life |
Sismo- graph: Seismographs
are instruments used to record the motion of the ground during an
earthquake.
Protection
during an earthquake
- 1. The
building should be designed so that they can resistant earthquake.
- 2. the
use of mud or Timber is better than the heavy construction material for making
the building in earthquake areas
- 3. cupboard and shelf should be fixed to the wall so that they do not fall on someone during an earthquake
Following
steps can be taken (indoors )
- 1. take
shelter under a table and stay till shaking stops stay away from tall and heavy
object
- 2. if
you are in bed do not get a protect your head with a pillow outdoors
- 3. find
a clear spot where buildings are away, trees and overhead power lines are away
Following
steps can be taken (outdoor)
- 1. if
you are in car or bus do not come out as the driver to drive slowly to a clear
spot do not come out till the timer stop
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