An electron moves along a vertical line and away from the observer. What is the pattern of the concentric circular magnetic field lines produced due to its motion?

The magnetic induction at point $O$ for the current-carrying wire shown in the figure is:

The magnetic induction at the centre $O$ of the current-carrying bent wire shown in the adjoining figure is

$A$ circular coil carrying current has radius $R$. The distance from the centre of the coil on the axis where the magnetic induction will be $\frac{1}{27}$th of its value at the centre of the coil is:

Consider a long straight wire of a circular cross-section (radius $a$) carrying a steady current $I$. The current is uniformly distributed across this cross-section. The distances from the centre of the wire's cross-section at which the magnetic field [inside the wire,outside the wire] is half of the maximum possible magnetic field,anywhere due to the wire,will be

The magnetic field at a distance of $10 \ cm$ from a long straight thin wire carrying a current of $4 \ A$ is (in $\mu T$)