hi friends in this video we are going to
see the concept of electric energy and
electric power and how it is related to
electrical parameters that is voltage
current and resistance so electrical
energy is nothing but electric work done
and it is given as V into Q where V is
the potential or voltage unit is volt
and Q is the charge unit is Coulomb so
all right see now we know electric
current is defined as rate of flow of
the charge so I can say I which is
electric current it is given as Q by T
where T is the time unit is second and I is
the electric current and unit is ampere
now this equation implies Q equals I
into T so let me write this as equation
number 1 this as an equation number 2
so if I substitute equation 2 in
equation 1 I will get all right here
from 1 and 2 I can say electric energy e
equals V I t
so if I know voltage if I know current
and amount of time for which this
electric current is passing through a
circuit I can get electric energy let me
write this equation in terms of
different parameters so once again I
will write electric energy is given as VIT
 now I am having one resistance and I
know current passing through it is I
because of that I am getting a voltage
across it as V so by Ohm's law I can say
V equals I into R again I will consider
say this is equation number three this
is equation number four so from three
and four I can have E as IR multiplied
by I into T which implies electric
energy equal to I square RT again by
Ohm's law I can say I I can consider as
v by R I will consider this other
equation number five and using equation
number three and five I can have
electric energy E equals V instead of I
I will substitute the v by r multiplied
by T this implies one more equation for
electric energy given as v square by r
into t
so if io voltage current of a circuit
and amount of time for which current is
passing I can use this expression for
electric energy but if I know current
resistance and amount of time I could
use this expression e equals I square RT
if I know voltage resistance and amount
of time for which I am applying the
voltage I can use expression of electric
energy as v square by r into t so it
depends upon what are the parameters
known to us as per that we have to use
the equation for electric energy
considering this fact
let's have equations for power also so i
will just write a definition of power
electric power is given as rate of doing
work rate of doing electric work or rate
of spending electric energy so it is
simply electric energy divided by time
so if I consider all these 3 equations I
have to just divide by T I will get
three more equations for the electric
power so Electric Power which is nothing
but P I can have three expressions in
terms of voltage and current that is
simply V into I in terms of resistance
and current it is I square R and in
terms of voltage and resistance it is v
square by r
the unit of power is what so I will have
here P equal to V into I P equal to I
square R and P equal to v square by R so
this will give you a hint
depends upon whatever the parameters
known to us either voltage and current
or voltage and resistance or current and
resistance I am able to use any one of
the expressions that I have mentioned
over here so here we have seen the
concept of electric energy and electric
power and how it is related to three
parameters that is voltage current and
resistance in subsequent videos we will
see how to use this formula and get a
answer which is asked thank you
