# Labelling nodes

1. Oct 21, 2008

### Altairs

1. The problem statement, all variables and given/known data
This is not a homework question but I still posted it here so that no one has any problems...

Today we had Electronics Lab and our teacher gave us the first lecture how to write a basic program for PSpice. She gave a circuit and asked us to write the program for it. (attached as picture). The problem came when she asked a mini-viva kinda thingy. She asked that what will you take at the tail of current source. +ive or -ive ? and why ? And guess what, no one knew the ans. Because there were just two possibilities so people took the signs randomly (in the hope that 50% chance will come out in their favor). And worst, she said that she will give the answer in next class which is a week away.

2. Relevant equations

Attached. Kindly identify all the polarities of the circuit elements.

3. The attempt at a solution

Completely blank. Simple. We havn't been told just how to deal woth current sources separately. Just no idea about these kind of problems.

Hope to learn it here.

Main problem was that we were confused that now there are two current sources. One the real current source and second the battery. What will be the effect now?

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2. Oct 22, 2008

### CEL

The labeling of the nodes is arbitrary. You put the plus sign wherever you want. The same is true for the direction of currents.
The associated labeling is when you attribute the direction of currents from the + to the - end of a branch. This convention is reversed when the branch contains a power source. In this case the current flows from - to +. So, the tail of the current source should be labeled -.