A circular coil has $35$ turns and a mean radius of $4.0 \mathrm{cm}$. It carries a current of $1.2 A$. Find the magnetic field (i) at a point on the axis of the coil at a distance of $40 \mathrm{cm}$ from its centre and (ii) at the centre of the coil.

A thick straight copper wire, carrying a current of $10 A$ is bent into a semicircular arc of radius $7.0 \mathrm{cm}$ as shown in Figure (a) (i) State the direction and calculate the magnitude of magnetic field at the centre of arc. (ii) How would your answer change if the same wire were bent into a semicircular arc of the same radius but in opposite way as shown in Figure (b)?

A long wire is bent, as shown in Figure. Find the magnitude and direction of the magnetic field at the centre $O$ of the circular part, if a current $I$ is passed through the wire.

Figure shows two semicircular loops of radii $R_1$ and $R_2$ carrying current $I$. Find the magnitude and direction of the magnetic field at the common centre $O$.

A circular segment of radius $10 \mathrm{cm}$ subtends an angle of $60°$ at its centre. A current of $9 A$ is flowing through it. Find the magnitude and direction of the magnetic field produced at the centre.

A current of $I$ ampere is flowing through the bent wire shown in Figure. Find the magnitude and direction of the magnetic field at point $O$.

In Figure, the curved portion is a semi‐circle and the straight wires long. Find the magnetic field at the point $O$.

A metallic wire is bent into the shape shown in Figure and carries a current $I$. If $O$ is the common centre of all the three circular arcs of radii $r, 2r$ and $3r$, find the magnetic field at the point $O$.