A Level Physics Notes: Electricity - 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 resistor
and
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 becauseand
are
in the same ratio as
and
Hence
We rearrange this to make
the
subject: