$A$ charged particle is moving in a uniform magnetic field in a circular path with radius $R$. When the energy of the particle is doubled,then the new radius will be

Two ions having same mass have charges in the ratio $1: 2$. They are projected normally in a uniform magnetic field with their speeds in the ratio $2: 3$. The ratio of the radii of their circular trajectories is -

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

$A$ particle of mass $m$ and charge $q$ has an initial velocity $\vec{v} = v_{0} \hat{j}$. If an electric field $\vec{E} = E_{0} \hat{i}$ and a magnetic field $\vec{B} = B_{0} \hat{i}$ act on the particle,its speed will double after a time:

$A$ current-carrying long solenoid is placed on the ground with its axis vertical. $A$ proton is falling along the axis of the solenoid with a velocity $v$. When the proton enters into the solenoid,it will

An electron is moving along the $+x$ direction. To make it move along an anticlockwise circular path in the $x-y$ plane,the magnetic field must be applied along: