Voltage between two wires?
Two wires connected to a voltage source of 10V (the polarity is of no importance here) have the same voltage over the whole length under the following conditions.


There is no flow of current (Not mentioned in the question).


Think also of this.

If there was a current you would need also the resistance of the wire expressed in Ohm/m and the distance of the 2 mm spot from the source. 


They do not touch each other (2mm distance as in the question)


Remember that the expression of fieldstrengh is V/m

The field strengh depends on the voltage and distance. Therefore in the question we have 10V/2mm = 5000 V/m.