$A$ charged particle enters a uniform magnetic field with a velocity vector making an angle of $30^o$ with the magnetic field. The particle describes a helical trajectory of pitch $x$. The radius of the helix is

In a region,there are uniform and constant electric and magnetic fields. Both these fields are parallel to each other. $A$ stationary charged particle is released in this region. The path of the particle will be.......

An electron,a proton,a deuteron,and an alpha particle,each having the same speed,are in a region of constant magnetic field perpendicular to the direction of the velocities of the particles. The radii of the circular orbits of these particles are respectively $R_e, R_p, R_d$,and $R_\alpha$. It follows that:

$A$ proton and an $\alpha$-particle enter a magnetic field perpendicularly with the same velocity. If the proton takes $25 \mu \text{sec}$ to complete $5$ revolutions,what is the time period of the $\alpha$-particle in $\mu \text{sec}$?

Particles having positive charges occasionally come with high velocity from the sky towards the earth. On account of the magnetic field of the earth,they would be deflected towards the

$A$ negatively charged particle projected towards east is deflected towards north by a magnetic field. The direction of the magnetic field is