試題詳解

11. A short solenoid (length I, radius a, ni turns per unit length) lies on the axis of a very one solenoid (length /, radius b, na turns per unit length), where a＜b. What is the total magnetic flux through the long solenoid if a steady current / flows in the short aD solenoid?
(A) μ₀πa²n₁n₂ll
(B) μ₀πb²n₁n₂ll
(C) μ₀πa²n₁²ll
(D)μ₀πabn₁n₂ll