Current $i$ is passed as shown in diagram. If radius of the circle is a, then the magnetic flux density at the centre $P$ will be:
$\frac{{{\mu _0}i\alpha }}{{4\pi a}} \otimes $
$\frac{{{\mu _0}i(2\pi - \alpha )}}{{4\pi a}} \otimes $
$\frac{{{\mu _0}i\,\sin \,\alpha }}{{2\pi a}} \otimes $
$\frac{{{\mu _0}i\,\sin \,\alpha }}{{4\pi a}} \otimes $
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
A coil having $N$ $turns$ carry a current $I$ as shown in the figure. The magnetic field intensity at point $P$ is
Two concentric coils each of radius equal to $2\pi \,{\rm{ }}cm$ are placed at right angles to each other. $3$ $ampere$ and $4$ $ampere$ are the currents flowing in each coil respectively. The magnetic induction in $Weber/{m^2}$ at the centre of the coils will be $({\mu _0} = 4\pi \times {10^{ - 7}}\,Wb/A.m)$
.......$A$ should be the current in a circular coil of radius $5\,cm$ to annul ${B_H} = 5 \times {10^{ - 5}}\,T$
Magnitude of magnetic field (in $SI$ units) at the centre of a hexagonal shape coil of side $10\, cm$, $50$ turns and carrying current $I$ (Ampere) in units of $\frac{\mu_{0} I}{\pi}$ is