Connecting wires carrying currents in opposite directions are twisted together in electrical appliances in order to reduce:

$A$ conducting wire carrying current $I$ is arranged as shown in the figure. Find the magnetic field at point $O$.

$A$ coil having $100$ turns is wound tightly in the form of a spiral with inner and outer radii $1 \text{ cm}$ and $2 \text{ cm}$,respectively. When a current $1 \text{ A}$ passes through the coil,the magnetic field at the centre of the coil is

In the diagram,$I_{1}$ and $I_{2}$ are the strengths of the currents in the loop and straight conductor,respectively. Given $OA = AB = R$. The net magnetic field at the centre $O$ is zero. Then the ratio of the currents in the loop and the straight conductor is:

Two long current-carrying conductors are placed parallel to each other at a distance of $8 \, cm$ between them. The magnitude of the magnetic field produced at the mid-point between the two conductors due to the current flowing in them is $300 \, \mu T$. The equal current flowing in the two conductors is ...............

$A$ circular coil is in the $y-z$ plane with its centre at the origin. The coil carries a constant current. Assuming the direction of the magnetic field at $x = -25 \, cm$ to be the positive direction of the magnetic field,which of the following graphs shows the variation of the magnetic field along the $x-$ axis?