Definition of Electric Charges:
Electric charge is a physical quantity which causes electric force in matter. When a glass rod is rubbed with a piece of silk cloth , the glass rod acquires the property of repelling another glass rod rubbed with silk cloth. It means , both glass rod when rubbed with silk cloth exert a force called electric force on each other.
This property of the objects by virtue of which they exert electric force on each other is related to electric charge.
Type of Electric Charges: Experiment :
Experiment 1: we conclude that two rubber rods rubbed with cat fur repel each other when brought near each other.
Experiment 2: we conclude that two glass rods rubbed with silk repel each other when brought near each other.
Experiment 3: we conclude that a glass rob rubbed with silk and rubber rod rubbed with fur attract each other when brought near each other.
By conclusion of these 3 experiment.
Franklin , as per convention who called the charge on a glass rod rubbed with silk as Positive charge (+ve or vitreous) and the charge on rubber rod rubbed with cat fur as negative charge (-ve or resin).
Atomic struture theroy : Reason of charge on body:
The study of atomic struture reveals that matter is electrical in nature means matter contains vast amount of charges (proton and electrons).
Under ordinary conditions, the body is electrically neutral because it contains equal amount of positive (Protons) and negative charges (Electrons).
When this equality or balance is disturbed by removing or supplying electrons , the body acquires a net charge.
Depending upon whether electrons are removed or added to a body , there are two types of charges.
(i) Positive charge (ii) Negative charge
If a glass rod is rubbed with silk , Some electrons pass from glass rod to silk. As result , the glass rod becomes positively charged and silk attains an equal negative charge
Like charges repels (Repulsion)each other while unlike charge attract (Attraction) each other.
S.I unit and CGS of Electric Charges :
SI unit of electric charge is coulomb (C).
Q = it
CGS unit of electric charge is Franklin , esu ( Electrostatics unit ) , Statcoulomb .
1 C = 3 ×10^9 Franklin ( esu )
Dimensions Formula of Electric Charges:
We know that formula of electric charge is
Q = it
[C] = [AT]