The magnetic field at the centre of a circular coil of radius $I$, due to current I flowing through it, is $B$. The magnetic field at a point along the axis at a distance $\frac{r}{2}$ from the centre is
$B / 2$
$2 B$
$\left(\frac{2}{\sqrt{5}}\right)^{3} B$
$\left(\frac{2}{\sqrt{3}}\right)^{3} B$
A uniform circular wire loop is connected to the terminals of a battery. The magnetic field induction at the centre due to $A B C$ portion of the wire will be (length of $A B C=l_1$, length of $A D C=l_2$ )
A coil of $50\, turns$ and $4\,cm$ radius carries $2\,A$ current then magnetic field at its centre is......$mT$
A current carrying loop consists of $3$ identical quarter circles of radius $\mathrm{R}$, lying in the positive quadrants of the $\mathrm{xy}$ , $\mathrm{yz}$ and $\mathrm{zx}$ planes with their centres at the origin, joined together. Find the direction and magnitude of $\mathrm{B}$ at the origin.
The unit vectors $\hat i,\;\hat j\;{\rm{and }}\,\hat k$ are as shown below. What will be the magnetic field at $O$ in the following figure