A negatively charged particle projected towards east is deflected towards north by a magnetic field. The field may be

A proton and an $\alpha -$ particle (with their masses in the ratio of $1 : 4$ and charges in the ratio of $1:2$ are accelerated from rest through a potential difference $V$. If a uniform magnetic field $(B)$ is set up perpendicular to their velocities, the ratio of the radii $r_p : r_{\alpha }$ of the circular paths described by them will be

An electron is moving along $+x$ direction. To get it moving along an anticlockwise circular path in $x-y$ plane, magnetic field applied along

A particle of mass $m,$ charge $Q$ and kinetic energy $K$ enters a transverse uniform magnetic field of induction $B.$ After $3$ $seconds$ the kinetic energy of the particle will be .......$K$

An electron is projected with velocity $\vec v$ in a uniform magnetic field $\vec B$ . The angle $\theta$  between $\vec v$ and $\vec B$  lines between $0^o$ and $\frac{\pi}{2}$ . It velocity $\vec v$ vector returns to its initial  value in time interval of 

A uniform beam of positively charged particles is moving with a constant velocity parallel to another beam of negatively charged particles moving with the same velocity in opposite direction separated by a distance $d.$ The variation of magnetic field $B$ along a perpendicular line draw between the two beams is best represented by