Page 145 - Science Class 08

ELECTRICAL CHARGES The charge of electrons and protons is

Benjamin Franklin was the first American measured in coulombs, represented by C.
scien st who proved that there are two types You have studied that when two materials all of
of electric charges — posi ve charge and different kinds are rubbed, they get electrified.
nega ve charge. It means they acquire electrical charges.

Electric charge is the property of sub-atomic However, the charges produced in this way are
par cles par cularly includes electrons and not always of the same kind. Depending on the
protons. Electrons have nega ve charge, nature of the objects rubbed together, a
protons have posi ve charge and neutrons do posi ve or a nega ve charge will be acquired
not have any charge. by them.
Let us do the following ac vi y to understand it:

Aim : To show that charges produced by rubbing depends on the nature of the objects
rubbed together.
Method:
Rub an ebonite rod with wool or flannel and hand it with a thread freely. Now, rub another
ebonite rod in the same way and bring it near the suspended rod. You will find that the two
ebonite rods repel each other.
Now, rub a glass rod with a piece of silk and bring it near the charged ebonite rod. The glass
rod will a ract the ebonite rod.
You can repeat this ac vity by bringing a charged glass rod near another suspended charged
glass rod. You will no ce the two charged glass rods will repel each other.

Now, you know that unlike electrical charges a ract each other while like charges repel each
other. A great scien st of the eighteenth century Benjamin Franklin gave specific names to
these charges. The charge on the glass rod was named as posi ve charge and the charge on the
ebonite rod was named as nega ve charge.

From the above men oned ac vity, you can If we bring two electrified objects in the same
make a table with one column lis ng substances column they will repel each other, but if they
acquiring a posi ve charge upon rubbing and are in different columns they will a ract each
another column containing substances acquiring other.
nega ve charges. ELECTRIC CHARGES IN ATOMS

You know that atom is the smallest par cle of
Posi ve charge Nega ve charge ma er. Electric charge is the basic property of
Glass rod Silk cloth the cons tuents of an atom. Each atom has a
centrally placed thing, nucleus in which almost
Woollen cloth Ebonite, rubber rod
the en re mass of it is concentrated. The
Woollen coat Plas c sheet
nucleus of an atom has neutrons and protons.
Woollen carpet Rubber shoes They are also called nucleus. The nucleus is

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