A toroidal transformer used in a modern audio system has N turns of copper wire going around a soft magnetic core as shown below. Is the magnetic field inside the toroidal transformer uniform? Why or why not? 

• A. The magnetic field inside is uniform because it has a constant radius.
• B. The magnetic field inside the toroid is NOT uniform, varying inversely with the radius
• C. The magnetic field inside the toroid is uniform regardless of the direction of the current.
• D. The magnetic field inside the toroid is NOT uniform, varying with the number of, N turns and current, I.

Answer: (B)