The Wheatstone bridge was invented by Samuel Hunter Christie in the year 1833 and was improved and popularized by Sir Charles Wheatstone in the year 1843.
Wheatstone bridge is widely used to measure the electrical resistance of circuits.
In this circuit, there are two known resistance, one unknown resistance and one variable resistance connected in this form.
IP is the current which passing through resistance P.
IQ is the current which passing through resistance Q.
IR is the current which passing through resistance R.
IS is the current which passing through resistance S.
IG is the current which passing through Galvanometer.
‘S’ is the variable resistor in this circuit.
By adjusting the variable resistor such that the current passing through the galvanometer became zero.
P/Q = R/S
R = PS/Q
Reference Source:
[1] Wheatstone Bridge Circuit Theory and Principle | Electrical4U. Electrical4U. Published February 24, 2012. Accessed March 1, 2022. https://www.electrical4u.com/wheatstone-bridge-circuit-theory-and-principle/
[2] Wheatstone Bridge – Working Principle, Formula, Derivation, Application. BYJUS. Published February 14, 2019. Accessed March 1, 2022. https://byjus.com/physics/wheatstone-bridge/