The magnetic field intensity $H$ at the centre of a long solenoid having $n$ turns per unit length and carrying a current $I$,when no material is kept in it,is

The expression for magnetic induction inside a solenoid of length $L$ carrying a current $I$ and having $N$ number of turns is

$A$ solenoid of $1.5 \ m$ length and $4.0 \ cm$ diameter possesses $10 \ turns/cm$. $A$ current of $5 \ A$ is flowing through it. The magnetic induction at the axis inside the solenoid is:

If the magnetic field inside a solenoid is $B$,then the magnetic energy stored in it per unit volume is (where $c$ is the speed of light in vacuum and $\varepsilon_0$ is the permittivity of free space).

$A$ solenoid has a core of a material with relative permeability $\frac{800}{\pi}$. The windings of the solenoid are insulated from the core and carry a current of $2 \text{ A}$. If the number of turns is $1000 \text{ turns/m}$, find the magnetic field $B$. (in $\text{ mT}$)

$A$ long solenoid carrying a current produces a magnetic field $B$ along its axis. If the current is doubled and the number of turns per cm is halved,the new value of the magnetic field is