Continuous charge distribution - Electric Charges & Fields Video Lecture - Class 12

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ahead with part 12 now we will discuss
about continuous charge distribution as
I told you before that charges are
discrete in nature right
according to quantization of charge but
when it is seen from a macroscopic level
then the discrete nature is lost and the
charge distribution appears continuous
like so here we will talk about the
different kind of continuous charge
distribution I mean how charges are
distributed in a body and the
distribution of however charge in itself
is discrete in nature but the
distribution of the charges on a body is
continuous so we will see what are the
different kinds of continuous different
types of continuous charge distribution
why I am discussing this this because
this is going to be useful as we go
ahead with different other topics
because till now we have just covered
electric charge and electric force but
we are yet to study about electric field
electric dipole and Gauss law so there
you will have this application so let us
study it before hand so what is
continuous charge distribution extremely
closed space charges form continuous
charge distribution as I told you before
also you remember the car example when
the cars as you go away from that view
of the car the cars appears more closer
to each other right so when you reach
out a very good height you can just see
those eight cars as a line why because
those cars are extremely closely spaced
that is why we are not able to
differentiate them separately as a
separate separate car so when some
charges are very closely spaced they
form a continuous charge distribution
because that time we are not able to
distinguish each charge separately they
all
I am present in cluster and the epical
and the entire thing is known as
continuous charge distribution so charge
so remember this point that charge is
still discrete charge is discrete in
nature that is a standard fact just that
the distribution is continuous so when I
talk of continuous charge distribution I
talk of charge density what is charge
density charge per unit dimension so
what is charge density let us suppose if
I have charges 1 2 3 4 5 6 7 8 9 10 11
12 13 14 15 so the other charges are
charges which are very closely spaced
together so what do I mean when I is a
charge density that means charge is
present per unit dimension so if it is
this area in this area how closely the
charges are placed that is known as
charge density so when I talk of charge
density there are three kinds of charge
density first is linear charge density
linear charge density talk it is
generally denoted by lambda it is linear
charge density basically talks about the
charge distribute so linear charge
density C is that the charge is present
per unit length right so here we
consider the scenario where the object
is a linear object let us suppose a rod
right so the number of charges present
per unit length of the rod so it is
generally denoted by lambda and it is
defined as lambda is equal to DQ / DL
where DQ is the number of charges
present and DL is the length of the
conductor so we write DQ is equal to
lambda D in she's let us suppose if this
is a very long conductor if you consider
a small portion of the conductor of
length DL then the number amount of
charge present in this length DL is
equal to lambda DL right so the next
kind
of charge density is superficial charge
density which is denoted by Sigma
superficial charge density is nothing
but charge per unit area so DQ by DA let
us suppose if I have a plain sheet a
very long infinite plain sheet let us
suppose if I consider a small area whose
area is da so how much is the charge
present in this area charge DQ present
in this area is given by Sigma into da
that Sigma is the superficial charge
density similarly the third type is
volumetric charge density which is
denoted by Rho so Rho is nothing but
charge per unit volume so DQ by DV let
us suppose instead of a plain sheet I
have a cube right so inside the cube
later suppose if I take a small volume
of volume DV so how much is the charge
enclosed in this small volume DV that is
given by DQ is equal to Rho DV right so
these are the various charge densities
which we come across this will be useful
when we try to calculate and when we
study about electric field you will have
application of these things so that is
why I taught this to you beforehand now
we will look at the force electrostatic
force in case of a conductor of length
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