Two very thin metallic wires placed along $X$ and $Y$-axis carry equal currents as shown in the figure. $AB$ and $CD$ are lines at $45^\circ$ with the axes,with the origin of the axes at $O$. The magnetic field will be zero on the line:

$A$ current carrying circular coil of radius $R$ produces magnetic field $B_1$ at an axial point $P$ at a distance $x$ from its centre and $B_2$ at point $Q$ placed at its centre respectively. If $B_2 = 8B_1$, the value of $x$ is

Two parallel wires carry currents $i_1$ and $i_2$ $(i_1 > i_2)$. When the currents are in the same direction,the magnetic field at a point midway between the wires is $10 \, \mu T$. When the direction of $i_2$ is reversed,the magnetic field at that point becomes $30 \, \mu T$. What is the ratio $\frac{i_1}{i_2}$?

Describe and illustrate the magnetic field lines produced by a current-carrying circular loop.

$A$ current $i$ flows through a square loop of side $a$. What is the magnetic field at its center?

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