physics
posted by Sandhya .
Two 10 meter long wires are parallel to each other and 5 cm apart.They carry currents of 6.0 A in opposite directions. What is the magnitude and direction of the magnetic field at a point P,halfway between the wires?
Calculate the force exerted by the left wire on the right wire. Indicate the direction of the force.

Parallel wires with currents in the same direction are attracted to each other. If the currents are in opposite directions, they repel.
If the currents are in opposite directions, the magnetic field along a line midway between them is twice the field due to a single wire.
The formulas you need can be found here:
http://theory.uwinnipeg.ca/physics/mag/node10.html