Science and Mathematics for Engineering 6th Edition by John Bird

Exercise 8

In a Wheatstone bridge PQRS, a galvanometer is connected between P and R, and a battery between Q and S. A resistor of unknown value is connected between P and Q. When the bridge is balanced, the resistance between Q and R is 150 , that between R and S is 25  and that between S and P is 500 . Calculate the value of the unknown resistance.