Answer:
81.2 A
Explanation:
The magnetic field at the center of a current-carrying loop is given by
[tex]B=\frac{\mu_0 I}{2R}[/tex]
where
[tex]\mu_0 = 4\pi \cdot 10^{-7} Tm/A[/tex] is the vacuum permeability
I is the current in the loop
R is the radius of the loop
In this problem, we have:
d = 12 cm is the diameter of the loop, so its radius is
R = d/2 = 12/2 = 6 cm = 0.06 m
[tex]B=0.85 mT=0.85\cdot 10^{-3}T[/tex] is the magnetic field at the center
Therefore, the current in the loop must be:
[tex]I=\frac{2RB}{\mu_0}=\frac{2(0.06)(0.85\cdot 10^{-3}}{4\pi \cdot 10^{-7}}=81.2 A[/tex]
