No, i am asked to find the locus of point where B=0, in any planeBut the problem you are given is to find all the points in the x-y plane where B=0.
He might be correct. But I don't interpret the question in that way. The magnetic field is undefined at the centre of the middle wire.i guess Phrak is right about the definition of thin in the question ...
I never said radius=0, I said radius tends to 0if we talk about wire with radius=0 ... how will there be any current through it? ... if there is place for current to pass then of course there will be a place to draw a gaussian surface
Even if radius --> 0 ... there will be some place through which current will travel ... it cant travel inside a simple line .... reember i=q/t ... q is charge crossing any surface perpendicular to wire in time tI never said radius=0, I said radius tends to 0
Move your perspective the X-Z plane. The wires are represented asi cant get you