Which of the following graphs correctly represents the variation of magnetic field $B$ with distance $R$ from a long straight current-carrying conductor?

Two wires $A$ and $B$ are of lengths $40 \ cm$ and $30 \ cm$. $A$ is bent into a circle of radius $r$ and $B$ into an arc of radius $r$. $A$ current $i_1$ is passed through $A$ and $i_2$ through $B$. To have the same magnetic inductions at the centre,the ratio of $i_1: i_2$ is

Consider a tightly wound $100$ turn coil of radius $10 \; cm$,carrying a current of $1 \; A$. What is the magnitude of the magnetic field at the centre of the coil?

The magnetic field at the centre of a circular coil of radius $R$ carrying current $I$ is $64$ times the magnetic field at a distance $x$ on its axis from the centre of the coil. Then,the value of $x$ is

$A$ straight wire carrying a current $10\, A$ is bent into a semicircular arc of radius $5\, cm.$ The magnitude of the magnetic field at the center is

The intensity of the magnetic induction field at the centre of a single turn circular coil of radius $5 \,cm$ carrying a current of $0.9 \,A$ is: