i=30A,B=4×10−4T r=2cm=2×10−2m Initial magnetic field (parallel to the wire), B1=4×10−4T Magnetic field produced by the straight wire, B2=
µ0
2πr
=
2×10−7×30
2×10−2
=3×10−4T B2 will be in the plane perpendicular to the plane of wire, so B1 and B2 are perpendicular to each other. ∴ Resultant magnetic field, B=√B12+B22 =√(4×10−4)2+(3×10−4)2 =5×10−4