Student "edition" found at {csi dot journalspace dot com}.

Maybe I shouldn't have started this blog now, not with everything that's been going on.

In the second meeting of my engineering Introduction to Electricity and Magnetism lecture class for the eleventh week of the first term, I gave them a more complicated example of a combination of series and parallel resistors and node and loop rule applications for more than one voltage source in a circuit. This time, it was a circuit that had two methods of solving, either in strictly node and loop rule applications or by reducing the resistors first using the principles of series and parallel.

I first solved it the first way, which although it seemed a bit intimidating at the start because they had to get six unknown currents, it was easily reduced to four because it turns out from the first two node equations shown that two of the currents were equal.

This, by the way, showed them that not all node equations could be counted, because from the first three, the fourth can be derived, which is actually what also happened with our previous example, that's why we could only solve it by getting one more loop equation that at the same time in total also used all of the branches of the circuit.

Also, if they chose their loops correctly, we ended up with one equation that only used one unknown current, and therefore could be solved directly.

The only problem was, substituting the value found in the other equations did not give us any new values, so there were more system of variables methods to use to determine the four remaining unknown currents.

Reducing the loops or branches without voltage sources to series and parallel equivalents first, we ended up with just three unknown current and two nodes (instead of four) which is relatively easier to solve.

The only confusion there was they had to learn that for parallel connections, currents solved are assumed to be splitting up from the parallel node, which was why one of the currents we computed from the first method had an opposite sign from the second one we solved, but still had the same value.

I told them it's up to them which method they chose for the exam.

Session 1245 has too many unknown currents. Class dismissed.