$A$ current $i$ flows in a circular arc of wire of radius $R$,which subtends an angle of $3\pi / 2$ radians at its centre. The magnetic induction at the centre is

Which of the following graphs shows the variation of magnetic induction $B$ with distance $r$ from a long straight wire carrying current?

For the magnetic field to be maximum due to a small element of a current-carrying conductor at a point,the angle between the element and the line joining the element to the given point must be.......$^o$

There are two infinitely long straight current-carrying conductors held at right angles to each other such that their common ends meet at the origin, as shown in the figure. The ratio of current in both conductors is $1:1$. The magnetic field at point $P(x, y)$ is:

$A$ circular loop of radius $0.0157\,m$ carries a current of $2.0\,A$. The magnetic field at the centre of the loop is $(\mu_0 = 4\pi \times 10^{-7}\,T\cdot m/A)$.

$A$ current of $0.1\, A$ circulates around a coil of $100$ turns and having a radius equal to $5\, cm$. The magnetic field set up at the centre of the coil is $({\mu _0} = 4\pi \times {10^{ - 7}}\,T\cdot m/A)$.