We have been doing a lot of work with wheatstone bridges in class lately and our teacher gave us a problem to try and I'm totally lost. The diagram that we were given has a 40 volt battery hooked to a wheatstone bridge circuit. The positive power flows into two resistors, one is 9 kiloohms and its opposite is unknown. The 9 kiloohm side then goes to a 5 kiloohm resistor and the unknown flows into a 12 after which the two sides rejoin and return to the 40 V battery. There is an ammeter across the bridge showing a current of 3 mA and we are asked to find the unknown resistance.(adsbygoogle = window.adsbygoogle || []).push({});

I've been working on this for about two hours and have come up with a lot of ideas that just don't work out. First I tried using kirchhof's rules but found that I had not voltage across the ammeter part of the bridge, so I tried assuming zero volts and came up short. Using my matrix math I came up with nothing.

I also tried solving the bridge as though it was balanced and figured out the overall total current and tried to use the 3 mA given to try and figure out what the four currents would be when its not balanced.

All the work we have done in class so far has been with balanced bridges or with a voltage across the bridge. This is the first time we have seen an unbalanced bridge with a current value. I'm totally lost and any push in the right direction would be great. Thanks for taking the time to read about my problem.

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# Wheatstone Bridge and battery

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