What happens to voltage when wire length increase?

When the length of the wire increases voltage drop across the wire will occur.

There are two factors that can result in voltage drop. One diameter of the wire, two length of the wire.

Voltage drop increases with increase in length of wire, whereas voltage drop decreases with increase in diameter (cross section area) of the wire.

G.RAO

If you are asking what happens to the voltage across a length of wire when its length increases, the answer is nothinghappens! The voltage applied to the wire is determined by the supply, not by the load (i.e. the wire).