Answer:
Distance for magnetic field at B position is r = 20 unit
Explanation:
As we know that magnetic field due to long wire is given as
[tex]B = \frac{\mu_0 i}{2\pi r}[/tex]
so here we can see that magnetic field is inversely depending on the distance from the wire
So we will have
[tex]\frac{B_2}{B_1} = \frac{r_1}{r_2}[/tex]
here we know that
[tex]B_1 = 200 unit[/tex]
[tex]B_2 = 50 unit[/tex]
[tex]r_1 = 5 unit[/tex]
so we have
[tex]\frac{50}{200} = \frac{5}{r}[/tex]
so we have
r = 20 units
