A charged particle enters a uniform magnetic field with 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
$\frac{x}{{2\pi }}$
$\frac{x}{{2\sqrt 2 \pi }}$
$\frac{x}{{2\sqrt 3 \pi }}$
$\frac{{\sqrt 3 x}}{{2\pi }}$
The time period of a charged particle undergoing a circular motion in a uniform magnetic field is independent of its
A uniform electric field and a uniform magnetic field are produced, pointed in the same direction. An electron is projected with its velocity pointing in the same direction
An electron is travelling in east direction and a magnetic field is applied in upward direction then electron will deflect in
An electron moving with a speed $u$ along the positive $x-$axis at $y = 0$ enters a region of uniform magnetic field $\overrightarrow B = - {B_0}\hat k$ which exists to the right of $y$-axis. The electron exits from the region after some time with the speed $v$ at co-ordinate $y$, then
A particle of charge $q$ and mass $m$ is moving with a velocity $-v \hat{ i }(v \neq 0)$ towards a large screen placed in the $Y - Z$ plane at a distance $d.$ If there is a magnetic field $\overrightarrow{ B }= B _{0} \hat{ k },$ the minimum value of $v$ for which the particle will not hit the screen is