Answer
The magnetic field strength at a distance d from the current carrying wire is given by $B=\frac{M_{0}I}{2\times pi\times d}$.
If d is doubled, then to maintain the magnetic field and reverse the direction, current needs to be doubled with its direction reversed.
Work Step by Step
The magnetic field strength at a distance d from the current carrying wire is given by $B=\frac{M_{0}I}{2\times pi\times d}$.
If d is doubled, then to maintain the magnetic field and reverse the direction, current needs to be doubled with its direction reversed.
