o Electricity
Electricity
is an important source of energy in the modern times.
Electricity
is used in our homes, in industry and in transport.
For
example, electricity is used in our homes for lighting, operating fans and
heating purposes. In industry, electricity is used to run various types of
machines, and in transport sector electricity is being used to pull electric
trains.
In
this chapter, we will discuss electric potential, electric current, electric
power and the heating effect of electric current. In order to understand
electricity.
we
should first know something about the electric charges.
Ø Electric Charges.
These
are discussed below. If we bring a plastic comb near some very tiny pieces of
paper, it will not have any effect on them. If, however, the comb is first
rubbed with dry hair and then brought near the tiny pieces of paper, we find
that the comb now attracts the pieces of paper towards itself.
These
observations are explained by saying that initially the comb is electrically
neutral so it has no effect on the tiny pieces of paper. When the comb is
rubbed with dry hair, then it gets electric charge. This electrically charged
comb exerts an electric force on the tiny pieces of paper and attracts them.
Similarly,
a glass rod rubbed with silk cloth ; and an ebonite rod rubbed with woollen
cloth also acquire the ability to attract small pieces of paper and are said to
have electric charge.
· Types of Electric Charges
It has
been found by experiments that there are two types of electric charges : positive charges and
negative charges.
(i)
Opposite charges (or Unlike charges)
attract each other. For example, a
positive charge attracts a
negative charge.
(ii)
Similar charges (or Like charges) repel
each other. For example, a positive charge repels a positive charge; and a
negative charge repels a negative charge.
The SI
unit of electric charge is coulomb which is denoted by the letter C.
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