Wheatstone bridge, c 1843.
© Science Museum / Science & Society Picture Library
The Wheatstone bridge is an electrical bridge circuit used to measure resistance. It consists of two potential dividers connected to a single battery. One divider is made up of the resistor to be measured and a resistor with a known value. The other is made up of two more known resistors. From this premise, the value of the unknown resistor can be found. Samuel Hunter Christie (1784-1865) was the first to describe the bridge in his publication 'Philosophical Transactions' in 1833. Sir Charles Wheatstone (1802-1875) came upon the description while researching electrical resistance as Profesor of Experimental Philosophy at King's College, London in 1843, and put the bridge method to practical application to measure the length of a wire by its resistance.