When a current flows through a solenoid,the solenoid acts as what?

The magnetic field $(B)$ inside a long solenoid having '$n$' turns per unit length and carrying current '$i$' when an iron core is kept in it,is ($\mu_0 =$ permeability of vacuum,$\chi =$ magnetic susceptibility).

$A$ solenoid of $1200$ turns is wound uniformly in a single layer on a glass tube $2\,m$ long and $0.2\,m$ in diameter. The magnetic intensity at the center of the solenoid when a current of $2\,A$ flows through it is:

What is a toroid? Obtain the formula for the magnitude of the magnetic field due to a current-carrying toroid.

$A$ solenoid is $1.0 \ m$ long and it has $4250$ turns. If a current of $5.0 \ A$ is flowing through it, what is the magnetic field at its centre? $[\mu_0 = 4\pi \times 10^{-7} \ T \cdot m/A]$

$A$ solenoid has a core of a material with relative permeability of $400$. The solenoid windings are insulated from the core and carry a current of $2 \text{ A}$. If the number of turns is $1000$ per meter,then the value of magnetic intensity will be . . . . . . .