$A$ current of $10\,A$ is passing through a long wire which has a semicircular loop of radius $20\,cm$ as shown in the figure. The magnetic field produced at the centre $P$ of the loop is:

Two concentric coils of $10$ turns each are placed in the same plane. Their radii are $20 \ cm$ and $40 \ cm$ and carry $0.2 \ A$ and $0.3 \ A$ current respectively in opposite directions. The magnetic induction (in $T$) at the centre is

The magnetic field at the centre of a current-carrying circular loop of radius $R$ is $16 \ \mu T$. The magnetic field at a distance $x = \sqrt{3}R$ on its axis from the centre is . . . . . . $\mu T$.

The magnetic field at the centre of a circular coil of radius $r$ carrying current $I$ is $B_1$. The field at the centre of another coil of radius $2r$ carrying the same current $I$ is $B_2$. The ratio $\frac{B_1}{B_2}$ is

$A$ circular current-carrying coil has radius $R$. The magnetic induction at the centre of the coil is $B_{C}$. The magnetic induction of the coil at a distance $\sqrt{3} R$ from the centre along the axis is $B_{A}$. The ratio $B_{A}: B_{C}$ is

Six very long insulated copper wires are bound together to form a cable. The currents carried by the wires are $I_1 = +10 \text{ A}, I_2 = -13 \text{ A}, I_3 = +10 \text{ A}, I_4 = +7 \text{ A}, I_5 = -12 \text{ A}$ and $I_6 = +18 \text{ A}$. The magnetic induction at a perpendicular distance of $10 \text{ cm}$ from the cable is (Given: $\mu_0 = 4\pi \times 10^{-7} \text{ T m/A}$) (in $\mu\text{T}$)