Answer:
The magnitude of the magnetic field at the center of the loop is 3.846 x 10⁻⁵ T.
Explanation:
Given;
number of turns of the flat circular loop, N = 18 turns
radius of the loop, R = 15.0 cm = 0.15 m
current through the wire, I = 0.51 A
The magnetic field through the center of the loop is given by;

Where;
μ₀ is permeability of free space = 4π x 10⁻⁷ m/A

Therefore, the magnitude of the magnetic field at the center of the loop is 3.846 x 10⁻⁵ T.