An electron moves along vertical line and away from the observer, then pattern of concentric circular magnetic field lines which are produced due to its motion

Two ions having masses in the ratio $1 : 1$ and charges $1 : 2$ are projected into uniform magnetic field perpendicular to the field with speeds in the ratio $2 : 3$. The ratio of the radii of circular paths along which the two particles move is

A particle of mass $m$ carrying charge $q$ is accelerated by a potential difference $V$. It enters perpendicularly in a region of uniform magnetic field $B$ and executes circular arc of radius $R$, then $\frac{q}{m}$ equals

An electron and a proton enter a magnetic field perpendicularly. Both have same kinetic energy. Which of the following is true

A uniform magnetic field $B$ is acting from south to north and is of magnitude $1.5$ $Wb/{m^2}$. If a proton having mass $ = 1.7 \times {10^{ – 27}}\,kg$ and charge $ = 1.6 \times {10^{ – 19}}\,C$ moves in this field vertically downwards with energy $5\, MeV$, then the force acting on it will be