PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Magnetism and Electromagnetism · Magnetism and Electromagnetism
Problem
Three conductors carry the same steady current I. (A) an infinitely long straight conductor, (B) a single-turn circular loop of radius R, and (C) a long solenoid wound with N turns over length ℓ where ℓ≫R. Each arrangement is considered at a point on its axis that is at the same distance R from the straight conductor in case A, at the centre of the loop in case B, and inside the solenoid in case C.
(i) Without performing any numerical calculation, state which of the three arrangements will give the weakest magnetic field at the specified point. Explain your answer qualitatively.
(ii) Identify which arrangement will give the strongest magnetic field and justify your choice on conceptual grounds.
(iii) Explain why the magnetic field inside a long solenoid is nearly uniform, whereas that near a straight conductor decreases rapidly with distance.