A Wheatstone bridge is a null measurement device that measures unknown resistance by balancing the potential drop. It comprises two parallel branches containing four resistors connected by a galvanometer, which acts as a bridge between them. The bridge circuit is connected to a voltage source. The circuit consists of two known resistors, a variable resistor and an unknown resistor. The variable resistance is tuned until the galvanometer reads zero. It implies that the potential at junction points of the central branch is the same, and no current flows through it. So, the two branches are in a parallel configuration and receive the same potential drop as the voltage source. Since junction points b and d have the same potential, the potential drop across R1 equals the drop across R3. Similarly, the potential drop across R2 equals the drop across Rx. Taking the ratio of these two equations yields an expression for the unknown resistor. Although this method is accurate, uncertainty in known resistance values and inaccurate zero current reading in the galvanometer causes measurement uncertainties.