A current-carrying coil represents

A particle moving in a magnetic field increases its velocity, then the radius of the circle

A proton and an alpha particle enter in a uniform magnetic field with the same velocity. The period of rotation of the alpha particle will be

An electron and a proton have equal kinetic energies. They enter a magnetic field perpendicularly, then

The strength of the magnetic field at a point distant $r$ near a long straight current carrying wire is $B$. The field at a distance $\frac{r}{2}$ will be

A long straight wire carries an electric current of $2 \mathrm{A}$. The magnetic induction at a perpendicular distance of $5 \mathrm{m}$ from the wire is

The magnetic induction at a point $P$ at distance $4 \mathrm{cm}$ from a long current carrying wire is ${10}^{-3 }\mathrm{T}$. The field of induction at a distance $12 \mathrm{cm}$ from the same current would be