Properties of electric charge

The
various properties of electric charge include:

• Additivity
  of charges

• Charge
  is conserved

• Quantization
  of charge

Additivity
of charges

If
a system contains two point charges q1 and q2,
then the total charge of the system is obtained by simply
adding q1 and q2, i.e., charges add
up like real numbers.

If
a system contains n number of charges q1, q2,
q3, q4, – – – – – – ,qn,
then
the total charge of the system is q1 + q2
+ q3 + q4 + – – – – – – – – + qn.

Charge
is a scalar quantity; it has magnitude but no direction,
similar to mass. However, there is one difference between
charge and mass. Mass of a body is always positive whereas
charge can be either positive or negative.

Let
us take for example, the system containing four charges q1
= +2C, q2 = +3C, q3 = -3C, q4
= +4C, then the total charge of the system is

               
q = q1 + q2 + q3 + q4

                  
= (+2) + (+3) + (-3) + (+4)

                  
= +6C

Therefore,
the total charge of the system is +6C and it is positively
charged.

Charge is
conserved

The law of
conservation of charge states that charge cannot be
created or destroyed. However, a charge can be
transferred from one object to other. 

Let us
consider two objects, object A and object B. Object A
has equal number of electrons and protons. So, it is
electrically neutral. Similarly, object B has equal
number of electrons and protons. So, it is also
electrically neutral.

When object
A and object B are rubbed with each other, negative
charges from object A can be transferred to object B.
Hence, object B has more number of electrons than
protons due to gaining of extra electrons. Similarly,
object A has lesser number of electrons than protons due
to losing of some electrons.

Therefore,
object A becomes positively charged and object B becomes
negatively charged. However, the total charge of an
isolated system remains constant.

Quantization
of charge

The
charge of any object is equal to integer multiples of the
elementary charge. This is known as quantization of
charge. It is given by

q = ne   (or)
  n(-e)

                       
Where q = electric charge of any object or body
                                   
n = any integer positive or negative
                                   
–

e

= elementary
charge = charge carried by single electron.
                                     

e

= elementary
charge = charge carried by single proton.

The
charge on an electron is written
as -e and charge
on a proton is written as +e.
The
quantization of charge was first suggested by the
experimental laws of electrolysis discovered by Faraday.
It was experimentally proved by Millikan. The total charge
on a object is equal to the algebraic sum of individual
charges present within the object.

If
an object contains n1 electrons and n2
protons, then the total charge on the object is n1

×

(-e)
+

n2

×

e

.
For example, if the object contains 150 electrons and 200
protons, then the total charge on the object is -150e
+ 200e = 50e.

Hence, the
object is positively charged. The object charge can be
exactly 0e or 1e, 2e – – – or -1e,
-2e – – – but not
1/2, 1/4 etc.