The Earth's magnetic induction at a certain point is $7 \times 10^{-5} \ Wb/m^2$. This is to be annulled by the magnetic induction at the center of a circular conducting loop of radius $5 \ cm$. The required current in the loop is......$A$

Two long straight parallel wires $A$ and $B$ separated by $5 \ m$ carry currents $2 \ A$ and $6 \ A$ respectively in the same direction. The resultant magnetic field due to the two wires at a point $P$ at a distance of $2 \ m$ from wire $A$ in between the two wires is:

$A$ charge $q$ moving in a circle of radius $r$ metre makes $n$ revolutions per second. The magnetic field at the centre of the circle is

$A$ charge $q$ $C$ moves in a circle at $n$ revolutions per second and the radius of the circle is $r$ $m$. The magnetic field at the centre of the circle is:

$A$ current $I$ flows in an anticlockwise direction in a circular arc of a wire having $\left(\frac{3}{4}\right)^{\text{th}}$ of the circumference of a circle of radius $R$. The magnetic field $B$ at the centre of the circle is $(\mu_0 = \text{permeability of free space})$

Apply the Biot-Savart law to find the magnetic field due to a circular current-carrying loop at a point on the axis of the loop.