Answer:
Telegraph distance will be 9.6 mile
Explanation:
We have given the voltage V = 9 volt
Contact resistance = 4 ohm
Relay resistance = 80 ohm
And wire has a resistance = 10 ohm/mile
We have given the current = 50 mA =0.05 A
According to ohm's law
So the resistance of wire = 180-4-80=96 ohm
So the length of the telegraph distance will be