# My brain is resistant to learning circuit analysis. Get it? Resistant? Like a resistor? Ahhh hahaha! Help.

October 31, 2012 3:11 PM Subscribe

I'm struggling in Electric Circuits 1 - particularly with analyzing series-parallel circuits, thevenizing and superposition. Before I look for a tutor, can anyone suggest some resources to learn it myself?

When I'm trying to analyze a circuit, I don't know where to start. I have a myriad of formulas and rules, but I don't know which I should apply to what, and in what order. There must be a step-by-step process for breaking it down and sorting through it, right? Or maybe it's just a question of bashing my head into it from different angles until I hit on the right one? My (universally disliked) professor puts an example on the board and then quickly solves it without explaining any kind of a process. I asked him for some help during our last lab and he just took my pencil and wrote down the answer. I said, "Give me a chance to do it on my own or I won't learn," and he just kind of chuckled.

Any suggestions?

When I'm trying to analyze a circuit, I don't know where to start. I have a myriad of formulas and rules, but I don't know which I should apply to what, and in what order. There must be a step-by-step process for breaking it down and sorting through it, right? Or maybe it's just a question of bashing my head into it from different angles until I hit on the right one? My (universally disliked) professor puts an example on the board and then quickly solves it without explaining any kind of a process. I asked him for some help during our last lab and he just took my pencil and wrote down the answer. I said, "Give me a chance to do it on my own or I won't learn," and he just kind of chuckled.

Any suggestions?

Here's another one -

Wikiversity- Elec Engrg.... and from that,

Wikiversity- Elec. Circuit Analysis

Hope that helps!

posted by drhydro at 3:45 PM on October 31, 2012

Wikiversity- Elec Engrg.... and from that,

Wikiversity- Elec. Circuit Analysis

Hope that helps!

posted by drhydro at 3:45 PM on October 31, 2012

Finding points of equal potential and drawing lines between them can be a useful trick to keep in the back of your mind as well. If two points are at equal potential then no current will flow through any new connection between them, which will therefore leave the circuit operation undisturbed; however, drawing those connections can sometimes let you simplify your algebra using the parallel-resistors formula.

The canonical puzzler that demonstrates this technique: consider a wireframe cube, each of whose edges has a resistance of 1 ohm. What is the resistance between any vertex and the one furthest from it?

Tackling that one the straightforward way involves a painful amount of algebra. Adding connections between points that symmetry shows must be at equal potential reduces the problem to finding the resistance of (three 1 ohm resistors in parallel) in series with (six 1 ohm resistors in parallel) in series with (three 1 ohm resistors in parallel).

There is at least some tiny chance that your universally disliked professor has not already seen this puzzle.

posted by flabdablet at 7:19 PM on October 31, 2012

The canonical puzzler that demonstrates this technique: consider a wireframe cube, each of whose edges has a resistance of 1 ohm. What is the resistance between any vertex and the one furthest from it?

Tackling that one the straightforward way involves a painful amount of algebra. Adding connections between points that symmetry shows must be at equal potential reduces the problem to finding the resistance of (three 1 ohm resistors in parallel) in series with (six 1 ohm resistors in parallel) in series with (three 1 ohm resistors in parallel).

There is at least some tiny chance that your universally disliked professor has not already seen this puzzle.

posted by flabdablet at 7:19 PM on October 31, 2012

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http://electron9.phys.utk.edu/phys136d/modules/m6/kirchhoff.htm

And you can check your answer by building the circuit with this simulator and checking the voltage drops and currents. (Or you can just blow up batteries when you get too frustrated.)

http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc

posted by BrashTech at 3:31 PM on October 31, 2012