Page 146 - Science Class 08
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surrounded by electrons. So, electrons, protons When an atom loses an electron, its electrical
and neutrons are the cons tuents of an atom. charges no longer balance or neutralise each
other. It is le with an excess of posi ve charge.
It is, therefore, called posi vely charged atom.
When an atom gains an extra electron, the
· Protons are posi vely charged. atom has an excess of nega ve charge. And the
· Neutrons do not have any kind of atom is said to be nega vely charged atom.
electric charge.
Now we can conclude that:
· Electrons are nega vely charged.
v A posi vely charged body is one which has
less number of electrons than protons.
The atom as a whole is electrically neutral
because the proton and the electron have v A nega vely charged body is one which has
equal and opposite charges and there are more electrons than protons.
exactly as many protons in the nucleus as v A body is said to be uncharged when it has
electrons outside. equal number of electrons and protons.
Ma er as a whole is ordinarily electrically
neutral – in any piece of ma er the posi ve
proton charges and the nega ve electron
charges cancel each other perfectly. 1. What is the meaning of the word electri-
city?
How do Ma er get Charged?
2. What is the difference between sta c
You studied that ma er as a whole is ordinarily electricity and current electricity?
electrically neutral. It means these are unchar-
3. What charges do atoms have?
ged. It is because the electrons and protons of
4. Why does a body become posi vely or
the atoms cancel the charges of each other. nega vely charged?
Then, how do ma er get charged on rubbing?
Let us find:
CHARGING A BODY
The electrons are bound by the protons present
Making a body to acquire property of a rac ng
in the nucleus. It is very difficult to dislodge
small objects is called charging or electrifi-
them. However, the outer most electrons are
ca on.
generally not firmly a ached to the atom of
which they are a part. A body can by charged by the following ways:
The applica on of heat may in certain cases By Rubbing
such violent mo on of the atomic par cles that When a body is rubbed with another body,
some of the outer electrons are torn away from both of them get charged. One of the bodies
the body of the atom. In other cases, the near acquires posi ve charge and the other acquires
presence of other bodies carrying large electric nega ve charge.
charges will tear some of the electrons loose. For example, when a glass rod is rubbed with a
Thus, an atom may lose electrons from another silk, the glass rod acquires posi ve charges and
atom.
146 Science-8
