Diameter of first wire (d1)=0.5mm Current in first wire (I1)=1A; Diameter of second wire (d2)=1mm and current in second wire (I2)=1A Strength of magnetic field due to current flowing in a conductor, (B)=
µ0
4π
×
2I
a
or B∝I. since the current in both the wires is same, therefore there is no change in the strength of the magnetic field.