Final answer:
The formula for the output voltage of a Wheatstone bridge is V = V₁ + V₂ + V₃. Each voltage drop is equal to the product of the current flowing through the resistor and the resistance value. By adjusting the variable resistance R₃ until the galvanometer reads zero, you can calculate the unknown resistance Rx.
Step-by-step explanation:
The formula for the output voltage of a Wheatstone bridge is V = V₁ + V₂ + V₃, where V is the voltage output of the source and V₁, V₂, and V₃ are the voltage drops across resistors R₁, R₂, and R₃ respectively.
Each voltage drop is equal to the product of the current flowing through the resistor and the resistance value, so V₁ = IR₁, V₂ = IR₂, and V₃ = IR₃.
By adjusting the variable resistance R₃ until the galvanometer reads zero, you can calculate the unknown resistance Rx based on the IR drops in the circuit.