The ammeter has an internal resistance of 0.02 Ohm, its scale is designed for a current of 1.2 A. Determine the resistance

The ammeter has an internal resistance of 0.02 Ohm, its scale is designed for a current of 1.2 A. Determine the resistance of the shunt that must be connected to the ammeter so that it can measure current up to 6 A?

Let us find the limiting voltage Um at the internal resistance of the ammeter if the internal resistance r is 0.02 Ohm, and the limiting current Im is 1.2 A:
Um = 1.2 * 0.02 = 0.024 V.
Let’s find the shunt current Ish, if the total current Io is 6 A:
Ish = Io – Im = 6 – 1.2 = 4.8 A.
Let’s find the resistance of the shunt Rsh:
Rsh = Um / Ish = 0.024 / 4.8 = 0.005 Ohm.
Answer: The shunt resistance should be 0.005 ohms.