Question

A loop of wire is in the shape of two concentric semicircles as shown. (Figure 1) 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 wire. What is the direction of the magnetic field at the center of the semicircles?

Question 4 A loop of wire is in the shape of two concentric semicircles as shown. (Eigure 1) The inner circle has radius a; the outer circle has radius b. A current flows clockwise through the outer wire and counterclockwise through the inner wire. igure Part A What is the magnitude, B, of the magnetic field at the center of the semicircles? Express B in terms of any or all of the following: I, a, b, and Ho 4a. ive Up Review Part Submi Hints My Answers Correct To see whether B n 1/a and B 1/b makes sense, think of the scaling of different quantities. The size of the current element scales as the radius whereas the power of r in the denominator is 2 (and equals the radius also, in this case). So over all, you would expect the magnetic field to scale as radius. Note that such an argument works only because the field due to each point is in the same direction, so you are doing a much simpler integral. Part B What is the direction of the magnetic field at the center of the semicircles? O into the screen O out of the screen My Answers Give Up Submit Provide Feedback Continue

Answer 1