Magnetic field due to a ring having $n$ turns at a distance $x$ on its axis is proportional to (if $r$ = radius of ring)

$A$ wire $A$, bent in the shape of an arc of a circle, carrying a current of $2 \, A$ and having radius $2 \, cm$, and another wire $B$, also bent in the shape of an arc of a circle, carrying a current of $3 \, A$ and having radius $4 \, cm$, are placed as shown in the figure. The ratio of the magnetic fields due to the wires $A$ and $B$ at the common centre $O$ is

$A$ non-planar loop of conducting wire carrying a current $I$ is placed as shown in the figure. Each of the straight sections of the loop is of length $2a$. The magnetic field due to this loop at the point $P(a, 0, a)$ points in the direction:

The adjoining figure shows a conductor carrying a current $i$. The magnetic field at the origin is

Five very long,straight wires are bound together to form a small cable. Currents carried by the wires are $I_1 = 20\,A, I_2 = -6\,A, I_3 = 12\,A, I_4 = -7\,A, I_5 = 18\,A.$ The magnetic induction at a distance of $10\,cm$ from the cable is

The magnetic field at the centre $O$ in the given figure is