When equal current is passed through two coils, equal magnetic field is produced at their centres. If the ratio of number of turns in the coils is $8: 15$, then the ratio of their radii will be

In the given figure net magnetic field at $O$ will be

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 ($\mu_0 = 4\pi \times 10^{-7} weber/amp-metre$)

Magnetic field vector component because of ...... and electric field scalar component because of ......

Two concentric coils $X$ and $Y$ of radii $16 \,\,cm$ and $10 \,\,cm$ lie in the same vertical plane containing $N-S$ direction. $X$ has $20$ $turns$ and carries $16 \,\,A.$ $Y$ has $25$ $turns$ $\&$ carries $18\,A$. $X$ has current in anticlockwise direction and $Y$ has current in clockwise direction for an observer, looking at the coils facing the west. The magnitude of net magnetic field at their common centre is

A portion of a conductive wire is bent in the form of a semicircle of radius $r$ as shown below in fig. At the centre of semicircle, the magnetic induction will be