Question

A very long, straight wire carries a constant current. The magnetic field a distance d from the wire and far from its ends varies with distance d according to

A) d^-3

B) d

C) d^2

D) d^-1

E) d^-2

Answer 1

for a long wire, magnetic field at a distance \(r\) is given by

$$ B=\frac{\mu_{0} I_{1}}{2 \pi r} $$

therefore, \(\mathrm{B}\) varies with d according to \(\mathrm{d}^{\wedge}-1\)

the correct option is D) \(\mathrm{d}^{\wedge}-1\)