Physics - Magnetism Question with Solution | TestHub

The magnetic field inside a long solenoid is given by $B=\mu nI$

where $\mu$ is the permeability of the medium inside the solenoid, $n$ is the number of turns per unit length, and $I$ is the current.

From the formula, the magnetic field $B$ is directly proportional to the permeability $\mu$ of the medium. Therefore, introducing a medium of higher permeability will increase the magnitude of the magnetic field.

The magnetic field of an ideal long solenoid is independent of its radius or area of cross-section, and decreasing the current would decrease the magnetic field.

Answer: introducing a medium of higher permeability