Question

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

• A. decreasing its radius
• B. decreasing the current through it
• C. increasing its area of cross-section
• D. introducing a medium of higher permeability
• E. decreasing the number of turns in it

Answer 1

Answer: (D)

By field along the axis of a solenoid
$B={\mu }_{0}ni$
where $B=$ magnetic field
${\mu }_0=$ permeability of free space
$n=$ the number of turns per unit length
$i=$ current
So, according to the formula,
The magnitude of the magnetic field inside a long solenoid is increased by introducing a medium of higher permeability.