An electron moving in a circular orbit of radius $r$ makes $n$ rotations per second. The magnetic field produced at the centre has a magnitude of

How can we determine the direction of the magnetic field using the Biot-Savart law?

Two infinitely long wires, each carrying a current $I = 10 \ A$, are bent to form a right angle as shown in the figure. Find the magnetic induction at point $O$. $\left[\mu_0 = 4\pi \times 10^{-7} \ H \ m^{-1}\right]$

Two concentric coplanar circular loops of radii $r_1$ and $r_2$ carry currents of respectively $i_1$ and $i_2$ in opposite directions (one clockwise and the other anticlockwise). The magnetic induction at the centre of the loops is half that due to $i_1$ alone at the centre. If $r_2 = 2r_1$,the value of $i_2/i_1$ is:

If a positive ion is moving away from an observer with some acceleration,then the lines of force of magnetic induction will be

If the strength of the magnetic field produced $10\,cm$ away from an infinitely long straight conductor is ${10^{ - 5}}\,Wb/m^2$,the value of the current flowing in the conductor will be........$A$.