Four wires meet at a junction. In two of the wires, currents and enter the junction. In one of the wires, current leaves the junction. Find the current in the fourth wire and indicate its direction.

Kirchoff's current law: It states that the total current entering at a junction is equal to the total current leaving at the junction. It isbased on conservation of charge.

As two current i1 and i2 is entering at the junction and i3 is leaving, so the current in forth wire is

i4 = i1 + i2 - i3