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

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

$A$ current carrying circular coil of radius $R$ has a point $P$ situated on its axis at a distance $x$ from its centre $O$ of the coil. The magnetic induction at point $P$ is $\left(\frac{1}{8}\right)^{\text{th}}$ of the magnetic field at its centre $O$. The value of $x$ is

$A$ current $I$ enters a circular coil of radius $R$,branches into two parts and then recombines as shown in the circuit diagram. The resultant magnetic field at the centre of the coil is

The magnetic field at a point $P$ situated at a perpendicular distance $R$ from a long straight wire carrying a current of $12 \ A$ is $3 \times 10^{-5} \ Wb/m^2$. The value of $R$ in $mm$ is $\left[\mu_0 = 4\pi \times 10^{-7} \ Wb/Am\right]$

$A$ long conducting wire having a current $I$ flowing through it is bent into a circular coil of $N$ turns. Then it is bent into a circular coil of $n$ turns. The magnetic field is calculated at the centre of the coils in both cases. The ratio of the magnetic field in the first case to that of the second case is: