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

Solenoid- It is a type of electromagnet which is used for the purpose to generate a controlled magnetic field through a coil wound into a tightly packed helix.

Complete step by step answer:
To generate a uniform magnetic field a long straight coil of wire can be used which is similar as a bar magnet. These coils are called solenoids. They have many practical applications. It is an essential coil of wire that is used in inductors, antennas, electromagnets, valves, etc. The applications are different in various types like locking systems,medical, industrial use etc. The field can be strengthened greatly by the addition of iron core. These cores are typical in electromagnets.

The magnetic field is concentrated into a nearly uniform field at the center of the solenoid. The field is weaker outside and the lines are further apart representing the magnetic field.
As we know that, The Expression for magnetic field is
$B = {\mu _0}\dfrac{{NI}}{l}$
Here, In the above formula we have
$B$=solenoid magnetic flux density
$l$=length of solenoid
$N$=number of turns per unit length
$I$=current
${\mu _0}$ = Magnetic Constant
Thus, According to the Formula
Thus, the magnitude of the magnetic field is increased by introducing a medium of higher permeability.
Correct Answer is Option D

Note: The permeabilities of most materials are very close to μ0, as most of the materials will be classified as either diamagnetic or paramagnetic. But in the ferromagnetic materials it is convenient to characterize the materials by a relative permeability as the permeability may be very large.