The field strength midway between two parallel wires carrying equal currents in the same direction will be

ZERO

Explanation:

As we know that magnetic field due to a straight wire at some distance from the wire is given as

so here since we have to find the magnetic field at the mid point of two parallel wire having equal current in them

so we can say

and since it is mid of of two wires so all the parameters will be same but the direction would be reversed as the mid point lies on the right side of one wire and on the left side of other wire.

now net magnetic field at mid point will be

this means that the temperature of both substances will be equal