$A$ negative charge is moving towards the observer. What will be the direction of the magnetic field produced by it,as seen by the observer?

$AB$ and $CD$ are long straight conductors,separated by a distance $d$,each carrying a current $I$. The magnetic field at the midpoint of $BC$ is

$A$ long straight wire carries an electric current of $2\,A$. The magnetic induction at a perpendicular distance of $5\,m$ from the wire is

$A$ tightly wound $100$ turns coil of radius $10 \,cm$ carries a current of $7 \,A$. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as $4 \pi \times 10^{-7} \,SI$ units):

The magnitude of the magnetic field (in $SI$ units) at the centre of a hexagonal coil of side $10 \, cm$, having $50$ turns and carrying a current $I$ (Ampere), in units of $\frac{\mu_{0} I}{\pi}$ is: (in $\sqrt{3}$)

Two long parallel wires carry currents $I_1$ and $I_2$ $(I_1 > I_2)$. When currents are flowing in the same direction,the magnetic field at a point midway between the wires is $6 \times 10^{-6} \ T$. If the direction of $I_2$ is reversed,the field at the midpoint becomes $3 \times 10^{-5} \ T$. The ratio $I_1 : I_2$ is