All straight wires are very long. Both $AB$ and $CD$ arcs of the same circle, both subtending right angles at the centre $O$. Then the magnetic field at $O$ is-

Identify the three field profiles that you measured for single coil $\left(\mathrm{Sgl}\right)$, Helmholtz coil $\left(\mathrm{Hh}\right)$ or Anti-Helmholtz coil $\left(\mathrm{A}-\mathrm{H}\right)$: The curves $A,B$ and $C$ are respectively:

Identical currents flow in two perpendicular wires, as shown in the figure. The wires are very close but do not touch. The magnetic field can be zero:

If the intensity of magnetic field at a point on the axis of current coil is half of that at the centre of the coil, then the distance of that point from the centre of the coil will be

Current flows through uniform, square frames as shown. In which case is the magnetic field at the centre of the frame not zero?

A conductor $PQ$ carries a current '$i$' is placed perpendicular to a long conductor $XY$ carrying a current $I$. The direction of force on $PQ$ will be

A circular current loop of radius a is placed in radial field $B$ as shown. The net force acting on the loop is

A write $PQRST$ carrying current $I=5 \mathrm{A}$ is placed in uniform magnetic field $B=2 \mathrm{T}$ as shown in fig. If the length of part $QR=4 \mathrm{cm}$ and $SR=6 \mathrm{cm}$ then the magnetic force on $SR$ edge of the wire is

A conducting rod of length $L$ and mass $m$ is moving down a smooth inclined plane of inclination $\theta$ with constant velocity $v$ in fig. A current $I$ is flowing in the conductor in a direction perpendicular to paper inwards. A vertically upward magnetic field $\overrightarrow{B}$ exists in space. Then magnitude of magnetic field $\overrightarrow{B}$ is