Wheatstone bridge—It is an arrangement of four resistance connected with galvanometer in the form of a bridge. It is used to find unknown resistance accurately.
Principle—If no electric current passed through galvanometer for balanced bridge, Ig = O
P/Q = R/5
Working theory—There are three resistance P, Q and R are but S is unknown. With the help of known resistance unknown resistance can be determined R is known resistance. If no electric current passed through galvanometer the bridge is said to be balanced.
Construction—
Equation (7) is the required condition for a balanced wheatstone bridge.
Advantages—
(i) It works on deflection method therefore is reading is very accurate.
(ii) In the help of known resistance unknown resistance can be determined in the order of high accuracy.
Disadvantage— It gives very accurate measurement only when all the resistance are nearly equal. It is extreamly difficult to select unknown resistance is the order of known resistance.
