Malla Reddy College of Engineering and Technology (MRCET)
Department of EEE ( 2017-18 )
Electrical Circuits EEE
Consider the circuit in fig(a), where two resistors are connected in parallel and therefore have
the same voltage across them. From Ohm’s law,
v
=
i
1
R
1
=
i
2
R
2
..................(1)
i
1 =
v
/
R
1,
i
2 =
v
/
R
2..................(2)
Applying KCL at node
a
gives the total current
i
as
i
=
i
1 +
i
2................(3)
Substituting Eq. (2) into Eq. (3), we get
i
=
v
/
R
1
+
v
/
R
2
=
v(1/R
1
+1/R
2
)
=v/
R
eq
1/Req=1/R
1
+1/R
2
Note:
The equivalent resistance of two parallel resistors is equal
to the product of their
resistances divided by their sum.
If "n"resistors are in parallel, 1/ Req=1/R1+1/R2+......1/Rn
If "n"resistors of same value are in parallel, Req=R/n
It is often more convenient to use conductance rather than resistance
when dealing with
resistors in parallel. The equivalent conductance for
N
resistors in parallel is
Dostları ilə paylaş: