Magnetic field at a distance $r$ from an infinitely long straight conductor carrying a steady current varies as

$A$ long straight wire carrying a current of $30\,A$ is placed in an external uniform magnetic field of induction $4 \times 10^{-4}\,T$. The magnetic field is acting parallel to the direction of the current. The magnitude of the resultant magnetic induction in tesla at a point $2.0\,cm$ away from the wire is

How can we determine the direction of the magnetic field using the Biot-Savart law?

Describe and illustrate the magnetic field lines produced by a current-carrying circular loop.

Charge $q$ is uniformly spread on a thin ring of radius $R.$ The ring rotates about its axis with a uniform frequency $f \ Hz.$ The magnitude of magnetic induction at the center of the ring is

In an ionised sodium atom,an electron is moving in a circular path of radius $r$ with angular velocity $\omega$. The magnetic induction in $Wb/m^2$ produced at the nucleus will be