SOME NATURAL PHENOMENA

IMPORTANT TERMS

Seismograph                A device used to measure seismic waves generated by earthquakes.

Seismology                  The study of earthquakes and seismic waves that move through and around the earth.

Seismologist                A scientist who studies earthquakes and seismic waves.

Electroscope                A device used to detect the presence and nature of electric charge on a body.

Lightning Conductor     A device used to protect buildings from the effects of lightning.

Nucleus                       The central portion of an atom that contains neutrons and protons.

Neutrons                      The particles that carry neutral charge in an atom. They are neither positive nor negative; are found in the nucleus of an atom.

Protons                        The positively charged particles in an atom. They are found in the nucleus of an atom.

Electrons                     The negatively charged particles in an atom. They travel in circular paths       around the nucleus of an atom.

Earthing                       Transfer of charge from a charged object to the earth.

Seismic Focus              The point at which the earthquake originates.

Epicentre                     The point at which the intensity of the earthquake is maximum.

Tsunami                      Giant waves caused by earthquake under the ocean.

 

ELECTRIC CHARGES

An object will attract another object only when it is electrically charged. If we move a plastic comb over bits of paper, they remain undisturbed because there is no charge either on the comb or on the bits of paper.

A charged object can attract an uncharged object and an oppositely charged object.

If two objects are brought close together and they attract each other, then it can be said that one of them is definitely charged and the other object might be neutral or bearing dissimilar charge. When a plastic comb is rubbed, it gets charged and can attract the bits of paper that are uncharged.

If two objects having the same type of charge are brought close together, they will always repel each other as ‘Like’ charges repel each other.

Unlike charges (positive-negative or negative-positive) always attract each other.

 

 

Like Charges           Positive-Positive (+ve and +ve)                             Repel

                                Negative-Negative (-ve and -ve)

 

 

Unlike Charges         Positive-Negative (+ve and -ve)                         Attract 

 

If an object has an excess of electrons after it gains electrons, then its electric charge would always be negative.

An object becomes positively charged when it has a deficit of electrons, after it loses electrons.

CHARGING AN OBJECT

An electrically neutral object can be charged by using any of the following methods:

Charging by Friction - Charging by friction involves rubbing one material with other. When two objects are rubbed together, they become charged due to the transfer of electrons from one object to another. E.g. when a glass rod is rubbed with a silk cloth, the glass rod is left with a positive charge and negative charge is acquired by the piece of silk. In this method, both the objects acquire equal and opposite charges.

Charging by Conduction - The method of charging by conduction involves a neutral object coming into direct contact with a charged object. During charging by conduction, both the objects, i.e. the charging and the charged body acquire the same type of charge. E.g. when we take a charged glass rod and touch it to a metal object, it (metal) will also get charged.

 

Charging by Induction- In the process of charging by induction, charging is done without touching the charged body to the object that has to be charged. For e.g. a charged glass rod is brought close to a metal object, but does not touch it. The metal object will also get charged. Through this method, the object acquires an opposite charge to that of the charging object.

Method of Charging	Process	Effect	Nature of Charge
Charging by Friction	Rubbing one material with other	Transfer of electrons from one object to another; both the objects are charged	E  Equal and opposite charges
Charging by Conduction	Direct contact with a charged object	A conductor gets charged by touching a charged object	Same nature of charge
Charging by Induction	Without touching the charged body	An uncharged object gets charged by bringing a charged body close to it	Opposite charge to that of the charging body

 

 

LIGHTNING

Lightning is a natural phenomenon that occurs because of electric discharge between two or more clouds or within the cloud or between clouds and the earth. The meeting of negative and positive charges produces streaks of light and sound, which is known as lightning. The accumulation of charges can flow from cloud to cloud, or cloud to ground, or between two portions of the same cloud.

Lightning is usually accompanied by rain and thunderstorms.

Lightning Conductors are used to protect buildings from the damaging effects of lightning. It is a metallic rod, which is installed in the walls of the building during its construction. One end of the rod is kept out in the air and the other is buried deep in the ground. If lightning strikes, this rod provides an easy route for the transfer of electric charge to the ground and protects the building.

Benjamin Franklin, an American scientist discovered the law of conservation of electric charge and proved that lightning is electricity.

 

SAFETY MEASURES AGAINST LIGHTNING STRIKES

Do not take shelter under a tree. Tall trees are more likely to be hit by lightning because of their height.

One should not carry an umbrella with a metallic handle during thunderstorm as metallic handle can be a potential target for lightning.

Try to take shelter indoors. A house or any other building is the safest place during lightning.

EARTHQUAKES

An earthquake is a natural phenomenon that occurs because of disturbance deep inside the earth's crust.

According to the theory of plate tectonics, the crust and the upper layer of the mantle (together known as lithosphere) is fragmented. It is divided into several 'plates' that move with respect to one another. The earth is divided into seven large plates and several smaller plates.

Vibrations caused by an earthquake travel in the form of waves along the surface of the earth. These waves are known as Seismic waves.

Earthquakes of high magnitudes (7.0 and above on Richter Scale) can cause serious damage to human life and property.

Richter scale is used to measure the magnitude of an earthquake. Charles Francis Richter, an American seismologist and physicist is known as the creator of the Richter magnitude scale.

It is not possible to predict the occurrence of an earthquake.

PROTECTION AGAINST EARTHQUAKES

Stay away from heavy objects.

If you are in a vehicle, stay inside.

If you are outside, stay away from buildings and tall trees.

One should never use an elevator during an earthquake but stairs to evacuate.

 

INTRESTING FACTS

 

• The temperature of a typical lightning bolt can reach 50,000 F degrees – that is 5 times greater than the temperature on the surface of the Sun.
• The energy contained in a single lightning strike can power a 100 Watt light bulb for 90 days.
• Lightning flashes more than 3 million times a day worldwide - that’s about 40 times a second. But all those flashes do not hit the ground; some of them happen between or inside clouds.
• The most powerful earthquake ever recorded on Earth was in Valdivia, Chile, which Occurred in 1960, and had a magnitude of 9.5.
• Coal is the biggest source of energy for producing electricity.
• An earthquake on the moon is called a moonquake. Moonquakes are generally weaker than earthquakes.
• According to the Hindu mythology, Earth is held in place by eight gigantic elephants, all are balanced on the back of turtle, which itself stands on the coils of a snake. If any of these animals shift or move, an earthquake occurs.