# lost

#### c0met

Joined May 21, 2008
2
i am lost on this circuit..can someone help me with this calculation. Thanks.

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#### mik3

Joined Feb 4, 2008
4,843
i am lost on this circuit..can someone help me with this calculation. Thanks.
You have to use start-delta transformations to make the resistances connected in series and parallel combinations to be able to find the equivalent.

#### Caveman

Joined Apr 15, 2008
471
It's not that hard actually. The left two are in series, so combine them. The result is parallel with another resistor, so combine those. The result is in series with another, so combine again, etc. Total of 4 cycles of series, then parallel should give the result.

Side note: From this pattern, you can develop an equation for an infinite ladder of resistors in this pattern. What do you think the answer is?

#### c0met

Joined May 21, 2008
2
618.18 ohms but this doesnt look right!

#### Caveman

Joined Apr 15, 2008
471
If you want to prove that it is right, assume a 1V power supply across the two nodes. Now work through the calculation of determining the different voltages and currents using nodal analysis. If the 618.18 is right, you will get 1V/618.18Ohms for the current from the 1V source.