What is Electrostatic is a new topic in which we talk you about electrostatic.
Study of charges at rest is called electrostatics or static
electricity. In this chapter, we will describe different
properties of static charges, such as electric force, electric
field and electric potential etc. We will also discuss some uses
and safety measures of static electricity.
If we run a plastic comb through our hair and then bring it
near small pieces of paper, the comb attracts them (Fig.13.1)
Similarly amber, when rubbed with silk, attracts the smal
pieces of paper. This property of attraction or repulsion
between substances is due to the electric charges they
acquire during rubbing.
We can produce electric charge by rubbing a neutral body
with another neutral body. The following activities show that
we can produce two types of electric charges through the
process of rubbing.
Acitivity 13.1.Take a plastic rod. Rub it with fur and suspend
it horizontally by a silk thread . Now take another
plastic rod and rub it with fur and bring near to the suspended
rod. We will observe that both the rods will repel each other.
It means during the rubbing both the rods were charged.
Acitivity 13.2.Now take a glass rod and rub it with silk and
suspend it horizontally. When we bring the plastic rod rubbed
with fur near to the suspended glass rod, we observe that
both the rods attract each other .
In the first activity, both rods are of plastic and both of them
have been rubbed with fur. Therefore, we assume that charge
on both rods would be of the same kind.
In the second activity, rods are unlike and their attraction
imply that charge on the two rods are not of the same kind
but of opposite nature.
These apposite charges are conventionally called positive
and negative charge. During the process of rubbing negative
charge is transferred from one object to another object.
From these activities we conclude that:
1. Charge is a basic property of a material body due to
which it attracts or repels another object.
2. Friction produces two different types of charge on
different materials (such as glass and plastic).
3. Like charges always repel each other.
4. Unlike charges always attract each other.
5. Repulsion is the sure test of charge on a body.
1. Do you think amount of positive charge on the glass
rod after rubbing with silk cloth will be equal to the
amount of negative charge on the silk? Explain.
2. What would happen if a neutral glass rod is brought
near a positively charged glass rod?