Network Theory Seminar (Part 3)


This time we use the principle of minimum power to determine what a circuit made of resistors actually does. Its ‘behavior’ is described by a functor sending circuits to linear relations between the potentials and currents at the input and output terminals. We call this the ‘black box’ functor, since it takes a circuit:

and puts a metaphorical ‘black box’ around it:

hiding the circuit’s internal details and letting us see only how it acts as viewed ‘from outside’.

For more, see the lecture notes here:

Network theory (part 32).


4 Responses to Network Theory Seminar (Part 3)

  1. e1211 says:

    The camera position is not good in this video compared to the other two, making the cameramen change the direction and the zoom a lot, which makes me dizzy. the other videos were much better in that sense.
    other than that, I really like the seminar, and i will keep watching it. thank you for filming it.

    • John Baez says:

      Thanks for the feedback!

      I’ll tell the cameraman. I’m not sure the position of the camera was worse; I think it was similar to the first video. In the second video the camera was more centered, but further away, and I thought my voice was hard to hear. So, in the third video I tried to put the camera in the same position as for the first video. Maybe the cameraman was just getting too excited about panning and zooming.

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