An ammeter with a current measurement limit Ilim = 3 A has some internal resistance r.

An ammeter with a current measurement limit Ilim = 3 A has some internal resistance r. When a 5/9 Ohm resistor is connected in parallel to the ammeter, the current measurement limit with this ammeter increases 10 times. Find the internal resistance of the ammeter. Express your answer in ohms.Let’s find the maximum total current that can flow through the ammeter with a shunt connected in parallel to it, equal to 5/9 Ohm, if the measurement limit of the ammeter without a shunt is 3 A, and with a shunt is 10 times more:

3 * 10 = 30 A.
Let’s find the current flowing through the shunt, if according to the ammeter it is equal to 3 A:
30 – 3 = 27 A.
Let’s find what the voltage is:
27 * 5/9 = 15 V.
Let’s find what the resistance of the ammeter is equal to:
15: 3 = 5 ohms.
Answer: the internal resistance of the ammeter is 5 ohms.