Some Natural Phenomena

Day and night, spring and autumn, raining & earthquake, rainbow and lighting are few examples of numerous natural phenomena. Some phenomena such as cyclones lighting and earthquake can cause a lot of damage to human life. Here, we will learn about various step which can minimize the adverse effect of these phenomena.

Also Check: Force

Before we proceed, we should know about ‘electric charge’. It is reason behind lighting. The concept of ‘what exactly charge is’ is beyond the scope of this module but should know, electric charge is property of this matter which is responsible for electrical phenomena. Electric charges exist is two forms:

1. Positive electric charge    
2. Negative electric charge

Electric Charge

Its story of about 2500 years ago, a Greek scientist called Thales observed that when a material known as 'amber' was rubbed with a silk cloth, it started attracting tiny feathers. Thales said that amber acquires electric charge (or electricity) on rubbing with silk. And the force of this electric charge attracts the tiny feathers.

Uncharged and Charged Objects

An object having no electric charge on it is called an uncharged object. An object having electric charge on it is called a charged object. A charged object attracts other uncharged objects. An uncharged object does not have any electric effect on other objects.

Also Check: Frictional Force

Charging an Object by Rubbing (or Friction)

The charging of an object by rubbing it with another object (such as silk cloth, woollen cloth, hair, paper or polythene, etc.) is called charging by friction. The charging of a glass rod by rubbing it with a silk cloth is an example of charging by friction.

When a plastic comb is rubbed with dry hair, the plastic comb acquires an electric charge due to friction. The plastic comb gets electrically charged. The electrically charged comb then attracts tiny pieces of paper. 

And when an inflated rubber balloon is rubbed with a piece of woolen cloth, it gets charged due to friction. The electric charges generated by rubbing (or friction) are static electric charges. These electric charges remain bound on the surface of the charged object.

 Friction Charges Both the Objects which are Rubbed Together

When two objects are rubbed together, then both the objects get charged by friction (but with opposite charges). For example, when a glass rod is rubbed with a silk cloth, then both, the glass rod as well as the silk cloth get charged. The charged glass rod can attract tiny pieces of paper and the charged silk cloth can also attract tiny pieces of paper. 

Also Check: Thrust & Pressure

How Rubbing Charges Various Objects

All the objects (like glass rod, silk cloth, rubber balloon, woollen cloth, plastic comb, hair, ballpoint pen refill, polythene etc.) are made up of tiny particles called atoms. All the atoms contain two types of electric charges inside them: positive electric charges called protons and negative electric charges called electrons. In an uncharged object, the number of positively charged particles (protons) and negatively charged particles (electrons) .n the atoms are equal. The equal number of electron and proton electric charges balance each other and make the object electrically neutral (having no over-all charge) protons are held strongly inside the nucleus of atoms, so protons cannot be transferred from the atoms of one object to another object during rubbing. But the negatively charged electrons are held loosely in the atoms (away from the nucleus), therefore, some of the electrons can be transferred from the atoms of one object to another object by rubbing.

1. The object which loses negatively charged electrons during rubbing, acquires a positive electric.
2. The object which gains negatively charged electrons during rubbing, acquires a negative electric charge. 

Depending on the nature of their electric charges, two charged objects may attract or repel each other.

1. If one object has positive charge and the other object has negative charge, then the two objects attract each other. In other words, unlike charges attract each other.
2. If the two objects have positive charges, they repel each other. 
3. If the two objects have negative charges, they repel each other. 

Many times when we take off woollen or synthetic clothes (like polyester and nylon cloths) our body hair stand erect on their ends. This is because rubbing (or friction) while taking off these clothes charges the body hair with the same kind of electric charge. Due to their like charges, the body hair repel one another. This repulsion makes the body hair stand erect. 

Also Check: Buoyant Force

Illustration 1: When a charged glass rod (rubbed with silk cloth) is brought near a charged Plastics straw (rubbed with polythene), there is attraction between the two. What is the nature of charge on the plastic straw?

Solution: By convention, the charge present on a glass rod (rubbed with silk cloth) is said to be positive (+). There can be attraction between a charged glass rod and a charged plastic straw only if their charges are opposite to each other. The opposite of positive charge is negative charge. So, the nature of charge on the plastic straw is negative (-).

Why a Charged Object Attracts an Uncharged Object

A charged object attracts an uncharged object by producing opposite charges in the nearer end of the uncharged object by electric induction. As an example, we will explain how a charged plastic comb attracts an uncharged piece of paper. Suppose a negatively charged plastic comb is held over a small piece of paper. The negatively charged plastic comb produces opposite charges (positive charges) in the top end of paper (which is nearer to it) by electric induction.

Also Check: Waves