The resistance of an ammeter is 13  Ω and its scale is graduated for a current up to 100 A. After an additional shunt has been connected to this ammeter it becomes possible to measure currents up to 7 50 A by this meter. The value of shunt resistance is

Let ia be the current flowing through ammeter and i the total current. So, a current i−ia will flow through shunt resistance.Potential difference across ammeter and shunt resistance is the same.⇒    ia ×  R=  i−ia  ×Sor     S=iaRi−ia                              …..(i)Given,  ia =100  A,  i=750 A,  R=13  ΩHence,   S=100  ×  13750 −100 = 2  Ω