Two straight long conductors $AOB$ and $COD$ are perpendicular to each other and carry currents $i_1$ and $i_2.$ The magnitude of the magnetic induction at a point $P$ at a distance $a$ from the point $O$ in a direction perpendicular to the plane $ACBD$ is

What will be the resultant magnetic field at origin due to four infinite length wires, if each wire produces magnetic field $\text{'}B\text{'}$ at origin

$AB$ and $CD$ are long straight conductor, distance $d$ apart, carrying a current $I$ The magnetic field at the midpoint of $BC$ is

Figure shows a square loop $ABCD$ with edge length $a$. The resistance of the wire $ABC$ is $r$ and that of $ADC$ is $2r$. The value of magnetic field at the centre of the loop assuming uniform wire is

Two thick wires and two thin wires, all of the same materials and same length form a square in the three different ways $P$, $Q$ and $R$ as shown in the figure with current connection shown, the magnetic field at the centre of the square is zero in cases.