A solenoid long is wound uniformly with turns of insulated wire and carries a current of
PHYSICS · Multi-part · AP · Physics C: Electricity and Magnetism · Magnetic Fields and Electromagnetism · Magnetic Fields and Electromagnetism
Problem
A solenoid 40cm long is wound uniformly with 800 turns of insulated wire and carries a current of 2.5A. The current enters the solenoid from the left end.
(i) Derive an expression for the magnetic field inside a long solenoid in terms of the permeability of free space μ0, the number of turns per unit length n, and the current I.
(ii) Using your expression, calculate the magnitude of the magnetic field inside the given solenoid.
(iii) Identify which end of the solenoid acts as a north pole. Explain your reasoning clearly.
(iv) The same wire is now rewound to make a solenoid of half the original length while keeping the same total number of turns and the same current. Calculate the new magnetic field inside it and comment on the change compared with part (ii).