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The Wheatstone Bridge

The Wheatstone Bridge is designed to enable the calculation of unknown resistances. It is very accurate, and works on reducing the potential difference or current between A and B to zero. It is much easier and more accurate to change the variable resistorand estimate when the current is zero than to measure the voltage across a resistor, the current though a resistor then use the equation

Having obtained a zero reading on the resistor, the unknown resistance R-x could then be calculated becauseandare in the same ratio asandHence

We rearrange this to makethe subject:

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