A long insulated copper wire is wound tightly on a cylindrical former to make a solenoid
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Magnetism and Electromagnetism · Magnetism and Electromagnetism
Problem
A long insulated copper wire is wound tightly on a cylindrical former to make a solenoid. The solenoid is many times longer than its diameter so that the magnetic field at its centre may be considered uniform.
(i) Define magnetic permeability and state its SI unit.
(ii) Explain, with suitable reasoning based on the contribution of individual turns, why the magnetic field inside the central region of such a solenoid is practically uniform and parallel to the axis.
(iii) A soft-iron core is now introduced into the solenoid. Explain qualitatively how and why the magnitude of the magnetic field changes.
(iv) Give a reasoned argument to show that the magnetic field near the open end of the same solenoid is approximately one-half of the field at its centre.