A light charged particle is revolving in a circle of radius '$r$' in electrostatic attraction of a static heavy particle with opposite charge. How does the magnetic field '$B$' at the centre of the circle due to the moving charge depend on '$r$' ?

Magnetic field induction at the centre of a circular coil shown in the figure is

A long solenoid carries current $I$. Curve between energy density (at mid-point of the solenoid) $E$ and $I$ is given by

A circular coil carrying current is placed in a region of uniform magnetic field acting perpendicular to the plane of the coil as shown in figure. The correct choice among the following is

The magnetic induction at point $C,$ if the current carrying wire is in the shape shown in the figure is

A proton of mass $m$ and charge $q$ is accelerated by a potential difference $V$ in a perpendicular magnetic field $B$ occupying space $t$. The value of $\sin \theta$ where $\theta$ is deviation of proton from initial direction is

A conductor of length $l$ is placed in $E-W$ direction on a plane. Earth's horizontal magnetic field is $B$. The amount of charge passed through it when it is found to jump to a height $h$ is

$\alpha$ particles, each of energy $2 \mathrm{MeV}$, are transmitted in a uniform magnetic field $B$. If the magnetic field is increased to double and deuterons are passed in the same system, the energy of a transmitted deuteron is given by

If the magnetic induction normal to the plane of a coil of n turns and radius $r$ carrying a current $I$ is measured on the axis of the coil at a small distance '$a$' from centre of coil, then fractional decrease in induction is