Thursday 14 February 2013
KCL & KVL
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Circuit :A Closed Path
Network :Inter Connection of Circuits
"Network Theory" is applicable only Low frequencies but not High Frequencies
For High Frequencies We have to go for "Field Theory"
NOTE : CURRENT ALWAYS GOES FROM HIGHER POTENTIAL TO LOWER POTENTIAL ie.,from positive to negative
NODE
In electrical engineering, node refers to any point on a circuit where two or more circuit elements meet
.
Kirchhoff's current law (KCL)
At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node,
or:
The algebraic sum of
currents in a network of conductors meeting at a point is zero.
IB + IC + ID = IA
Bringing everything to the left side of the above equation, we get
(IB + IC + ID) - IA = 0
NOTE
INCOMING CURRENTS ARE TAKEN AS NEGATIVE
OUTGOING CURRENTS ARE TAKEN AS POSITIVE
IMPORTANT POINTS
1.Charge can neither be created nor destroyed.so it follows law of conservation of charge
Let's examine a circuit simulation. It's shown below. Charge (current) is flowing through the circuit. The simulation shows some charge - the large red blob - flowing through a battery (where it picks up energy, but that's another story. Click here for that lesson.) That charge flows through Element #1 in the simulation. After the charge flows through Element #1 it splits. Some of the charge goes through Element #2, and some goes through Element #3. (Notice that it does not split equally! Sometimes it does. Sometimes it doesn't.) When, in the course of its flow through the circuit, there is no possibility of splitting, all of the charge entering a node will flow through the next element. (That element is said to be in series. Element #3 and Element #4 are in series because all of the current going through #3 goes through #4. Elements #1 and #2 are not in series.)
There is one node in the simulation where charge flowing through two elements comes together and "reunites" and flows back into the battery.
IMPORTANT POINTS
1.Charge can neither be created nor destroyed.so it follows law of conservation of charge
Let's examine a circuit simulation. It's shown below. Charge (current) is flowing through the circuit. The simulation shows some charge - the large red blob - flowing through a battery (where it picks up energy, but that's another story. Click here for that lesson.) That charge flows through Element #1 in the simulation. After the charge flows through Element #1 it splits. Some of the charge goes through Element #2, and some goes through Element #3. (Notice that it does not split equally! Sometimes it does. Sometimes it doesn't.) When, in the course of its flow through the circuit, there is no possibility of splitting, all of the charge entering a node will flow through the next element. (That element is said to be in series. Element #3 and Element #4 are in series because all of the current going through #3 goes through #4. Elements #1 and #2 are not in series.)
There is one node in the simulation where charge flowing through two elements comes together and "reunites" and flows back into the battery.
Note that
this simulation emphasizes the conservation of charge. When charge
flows through Element #1 when it gets to the end of Element #1 it splits
into two. However, what arrives at that node is what leaves that node,
so the amount of charge that enters the node - the big red blob -
equals the amount of charge that leave that node - the sum of the charge
on the medium sized red blob and the charge on the small red blob.
2) kcl is applied to linear,nonlinear,active,passive, bilateral ,time variant and time invariant circuits
3)it is independent of nature of element connected to node
4) kcl is valid to any lumped electric circuit at constant temperature
2) kcl is applied to linear,nonlinear,active,passive, bilateral ,time variant and time invariant circuits
3)it is independent of nature of element connected to node
4) kcl is valid to any lumped electric circuit at constant temperature
Kirchhoff’s Voltage Law (KVL):
The algebraic sum of the voltages around any closed path is zero.
EXAMPLE
V1-V2-V3-V4=0
IMPORTANT POINTS
1) it follows law of conservation of energy
2) it is valid for lumped electric circuit at constant temperature
3) independent of nature of element
4) KCL is applied to linear,nonlinear,active,passive, bilateral ,time variant and time invariant circuits
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