試題詳解

18. A long straight very thin wire on the y-axis carries a 10-A current in the positive y-direction. A circular loop 0.50 m in radius, also of very thin wire and lying in the yz-plane, carries a 9.0-A current, as shown. Point P is on the positive x-axis, at a distance of 0.50 m from the center of the loop. What is the magnetic field vector at point P due to these two currents? (μ₀ =4πx 10^-7 T m/A)
(A) zero
(B) -8.0 x10^-6Tk
(C)(+4.0x10^-6T)i- (4.0 x10^-6T)k
(D) (-8.0x10^-6T)i - (8.0 x 10^-6T)k
(E)(-4.0x10^-6T)i-(4.0 x10^-6T)k