The unit of magnetic induction is

$A$ uniform circular wire loop is connected to the terminals of a battery. The magnetic field induction at the centre due to $ABC$ portion of the wire will be (length of $ABC = l_1$, length of $ADC = l_2$):

$A$ long straight wire carrying electric current $i$ is bent at its mid-point to form an angle of $45^{\circ}$ as shown in the figure. The magnetic field at a point $P$ at a distance $d$ from the point $Q$ of bending is:

$A$ current of $8 \text{ A}$ each flows in opposite directions in two parallel conducting wires placed at a distance of $30 \text{ cm}$. The magnitude of the magnetic field at the midpoint between the two wires is . . . . . . $\mu \text{T}$. (Given: $\frac{\mu_0}{4\pi} = 10^{-7} \text{ N/A}^2$)

Two long parallel wires are at a distance $2d$ apart. They carry steady equal currents flowing out of the plane of the paper as shown. The variation of magnetic field $B$ along the line $XX'$ is given by

The magnitude of the force per unit length acting on a thin wire carrying a current $I=8 \text{ A}$ at a point $O$, if the wire is bent as shown in the figure with a radius $R=10 \pi \text{ cm}$, is (in $\mu \text{N/m}$)