what is an essential node??

[Semidevil]

so lets say here is a simple circuit:


http://www.geocities.com/hluu410/circuit.bmp

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ok, so the black O's represent the nodes. and the / and \ represents the resistors...there is a voltage source and current source.

Looking at this,, I see there are 4 nodes. An essential node is a node with 3+ elements connected correct? all the nodes there have 3 things connected to it, so therefore, there are 4 essential nodes. right?

WRONG.

my book says that this circuit has 3 essential nodes. I can't see how there are 3 essential nodes instead of 4 nodes? If I can't get this fixed up, I wont be able to go through the rest of the problems...

so exactly which 3 are the essential nodes?

edit: link pic link
edit again: link no work..........needs to cut/paste..

 

[KMurphy]

An essential node is where current is doing more than going in one point and out another. There are typically three or more directions for current to flow in an essential node for DC circuits .

EDIT:
That diagram doesn't do much to help your question either.

 

[KMurphy]

Those two nodes at the bottom make a super node since they share a common reference. There is no voltage drop between them.

 

[Semidevil]

so looking at the pic, which 3 of those 4 are essential nodes? they all look the same too me........

 

[Yomicron]

Originally posted by: KMurphy
Those two nodes at the bottom make a super node since they share a common reference. There is no voltage drop between them.

A super node has a dependent source between the 2 nodes. Those 2 bottom "nodes" are actually a single node because they are shorted together.

EDIT: You can redraw the circuit

 

[RaynorWolfcastle]

Originally posted by: Yomicron

Originally posted by: KMurphy
Those two nodes at the bottom make a super node since they share a common reference. There is no voltage drop between them.

A super node has a dependent source between the 2 nodes. Those 2 bottom "nodes" are actually a single node because they are shorted together.

A supernode is actually anything that has more than one "non-super" node in it. You could have a a super-node in which you have a current source, a voltage source and numerous resistors. A supernode is just KCL applied to a portion of a circuit that is larger than a single node.


your 2 bottom nodes are actually 1 node (call it the circuit common if you like) the bottom is essential, and each of the top node is essential. Basically a node is essential if it isn't trivial.

 

[Semidevil]

Originally posted by: RaynorWolfcastle

Originally posted by: Yomicron

Originally posted by: KMurphy
Those two nodes at the bottom make a super node since they share a common reference. There is no voltage drop between them.

A super node has a dependent source between the 2 nodes. Those 2 bottom "nodes" are actually a single node because they are shorted together.

A supernode is actually anything that has more than one "non-super" node in it. You could have a a super-node in which you have a current source, a voltage source and numerous resistors. A supernode is just KCL applied to a portion of a circuit that is larger than a single node.


your 2 bottom nodes are actually 1 node (call it the circuit common if you like) the bottom is essential, and each of the top node is essential. Basically a node is essential if it isn't trivial.

so basically, the 2 nodes at the bottom are 1 node, because there is no element between them?? am I correct?

 

[Yomicron]

Originally posted by: RaynorWolfcastle

Originally posted by: Yomicron

Originally posted by: KMurphy
Those two nodes at the bottom make a super node since they share a common reference. There is no voltage drop between them.

A super node has a dependent source between the 2 nodes. Those 2 bottom "nodes" are actually a single node because they are shorted together.

A supernode is actually anything that has more than one "non-super" node in it. You could have a a super-node in which you have a current source, a voltage source and numerous resistors. A supernode is just KCL applied to a portion of a circuit that is larger than a single node.


your 2 bottom nodes are actually 1 node (call it the circuit common if you like) the bottom is essential, and each of the top node is essential. Basically a node is essential if it isn't trivial.

I stand corrected, but it still isn't a supernode, as it only is a single node.

 

[Yomicron]

Originally posted by: Semidevil
so basically, the 2 nodes at the bottom are 1 node, because there is no element between them?? am I correct?

correct

 

[Semidevil]

Originally posted by: Yomicron

Originally posted by: Semidevil
so basically, the 2 nodes at the bottom are 1 node, because there is no element between them?? am I correct?

correct

cool
thanx very much guys.