Gauss is unit of which quantity

A long straight wire, carrying current $I$ is bent at its mid-point to form an angle of $45^{\circ}$. Induction of magnetic field (in tesla) at point $P$, distant $R$ from point of bending is equal to

$B _{ X }$ and $B _{ Y }$ are the magnetic field at the centre of two coils of two coils $X$ and $Y$ respectively, each carrying equal current. If coil $X$ has $200$ turns and $20 cm$ radius and coil $Y$ has $400$ turns and $20 cm$ radius, the ratio of $B _{ X }$ and $B _{ Y }$ is

Current $i$ is passed as shown in diagram. If radius of the circle is a, then the magnetic flux density at the centre $P$ will be:

A very long wire $ABDMNDC$ is shown in figure carrying current $I. AB$ and $BC$ parts are straight, long and at right angle. At $D$ wire forms a circular turn $DMND$ of radius $R. AB.$ $\mathrm{BC}$ parts are tangential to circular turn at $\mathrm{N}$ and $D$. Magnetic field at the centre of circle is

An infinitely long straight conductor is bent into the shape as shown in the figure. It carries a current of $i$ $ampere$ and the radius of the circular loop is $r$ $metre$. Then the magnetic induction at its centre will be