Question

A power station supplies a factory 400 m away by two wires. The potential difference between the terminals at the factory is 220 volt and the current flowing through it is 80 ampere. Calculate the potential difference at the station given that the resistance of one meter of the wire is 5*(10^-4) ohm/m

Answer 1

You would have 800 meters of wire, the resistance would be then 800(5 *.0001) or approximately .4 Ohms (i say approximately as there would be the resistance of the terminal connections etc.) The voltage loss would then be E=IR, or 80* .4=32 volts. The voltage at the factory terminals would then be 188 volts.
If the factory equipment required 220 volts then a transformer could be used to step it up.

Answer 2

What will the resistance at the station be? That's the question.

Answer 3

The written problem asks for the "Potential Difference" at the station, I misread the problem and thought the station was supplying 220V and it was asking for the potnetial difference at the factory. My bad.

You merely add the 32 volts to the 220 and that will give you the voltage at the station.
Same principal.

Now apparently you are asking for the resistance offered by the station. Use Ohm's law
R=E/I where E= The station voltage, and I= 80 Amperes.