試題詳解

4. Consider an infinite wire carrying a current I as shown in the figure. The curve is a semicircle of radius a. What is the magnetic field at the center of the semicircle P? μ₀ is the vacuum permeability.

(A)(π + 1)
(B)(π + 2)
(C)(2π + 1)
(D)(2π + 2)
(E) none of the above