The magnitude of the magnetic field inside a long solenoid is increased by

Options

A. decreasing its radius
B. decreasing the current throught it
C. increasing its area of cross section
D. introducing a medium of higher permeability

Answer

D

Explanation

By field along the axis of a solenoid `B=mu_(0)ni`
The magnitude ot the magnetic field inside long solenoid is increased by introducing a medium of higher permeability