$A$ long solenoid with $20$ turns per $cm$ is made. To produce a magnetic field of $20$ $mT$ inside the solenoid, the necessary current will be approximately......$A$.

Using Ampere's circuital law,derive the expression for the magnetic field at a perpendicular distance $r$ from an infinitely long current-carrying wire. Explain it.

$A$ long solenoid has $n$ turns per meter and current $I \ A$ is flowing through it. The magnetic field at the ends of the solenoid is

What is a solenoid? Provide information about the magnetic field through a qualitative discussion.

$A$ solenoid of $1 \ m$ length and $3.55 \ cm$ inner diameter carries a current of $5 \ A$. If the solenoid consists of five closely packed layers each with $700$ turns along its length,then the magnetic field at its centre is (in $mT$)

$A$ cylindrical conductor of radius $R$ is carrying a constant current. The plot of the magnitude of the magnetic field,$B$ with the distance $d$,from the centre of the conductor,is correctly represented by the figure: