$A$ toroid is:

Rank the value of $\oint \vec{B} \cdot d\vec{l}$ for the closed paths shown in the figure from the smallest to largest.

$A$ 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

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).

The number of turns per unit length of a long solenoid is $10 \, \text{turns/cm}$. If its average radius is $5 \, \text{cm}$ and it carries a current of $10 \, \text{A}$, then the ratio of flux densities obtained at the centre and at the end on the axis will be:

$A$ toroid has $500$ turns per metre length. If it carries a current of $2 \text{ A}$, the magnetic energy density inside the toroid is: (in $\text{ J/m}^3$)