The current of $5 \mathrm{~A}$ flows in a square loop of sides $1$ $\mathrm{m}$ is placed in air. The magnetic field at the centre of the loop is $\mathrm{X} \sqrt{2} \times 10^{-7} \mathrm{~T}$. The value of $\mathrm{X}$ is____.

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

Show magnetic field lines due to current carrying loop.

A vertical straight conductor carries a current vertically upwards. A point $P$ lies to the east of it at a small distance and another point $Q$ lies to the west at the same distance. The magnetic field at $P$ is

A straight wire of diameter $0.5\, mm$ carrying a current of $1\, A$ is replaced by another wire of $1\, mm$ diameter carrying the same current. The strength of magnetic field far away is

A charge $q$ $coulomb$ moves in a circle at $n$ revolutions per second and the radius of the circle is $r$ $metre$. Then magnetic field at the centre of the circle is