about the kirchoffs laws

1. KIRCHOFF’S LAW
P.VEENA TANMAI
227R1A1246
IT(A)

2. TYPES OF LAWS:
KIRCHOFF’S
LAWS
KIRCHOFF’S
CURRENT
LAW(KCL)
KIRCHOFF
’S
VOLTAGE
LAW(KVL)
These laws are first derived by “Guatov
Robert Kirchoff” and hence these laws are
also referred as Kirchoff Laws.

3. CIRCUIT DEFINITIONS
Node- any point where 2 or more circuit
elements are connected together
• Wires usually have negligible resistance
• Each node has one voltage (w.r.t ground)
Branch- a circuit element between two
nodes
Loop-a collection of branches that form a
closed path returning to the same node
without going through any other nodes or
branches twice

4. IDENTIFICATION OF MESHES AND NODES

5. KIRCHOFF’S CURRENT LAW(KCL)
 The algebraic sum of currents entering a
node is zero
 Add each branch current entering the node
and subtract each branch current leaving
node
 ∑ currents in -∑ currents out =0
 Or ∑ currents in = ∑ currents out
Then, the sum of all the currents is zero.
This can be generalized as follows

7. IDEAL CURRENT SOURCE

8. Example
• Find the current through 8Ω resistor using
KIRCHROFF’S LAWS.

9. 1)No. of meshes =3
2)Asssigned currents= i1,i2,i3
3) By applying kvl in mesh 1
10= -6i1-5(i1-i2)
10=-6i1-5i1+5i2
10=-11i1+5i2(1)
by applying kvl in mesh 2
-5(i2-i1)-3i2-4(i2-i3)=5
-5i2+5i1-3i2-4i2+4i3=5
5i1-12i2+4i3=5(2)

10. By applying kvl in mesh 3
-4(i3-i2)-2i3=-5
-4i3+4i2-2i3=-5
4i2-6i3=-5(3)
Therefore;
i1=-1.3A
i2=-0.9A
i3=0.2A

11. THANKYOU