Item 4 Part A A loop of wire is in the shape of two concentric semicircles as shown. ( Figure 1) What is the magnitude, B, of the magnetic field at the center of the semicircles? The inner circle has radius a; the outer circle has radius b. A current I flows clockwise through the outer wire and counterclockwise through the inner Express B in terms of any or all of the following: I, a, b, and Mo. wire. View Available Hint(s) LL AED X