An electron enters a magnetic field whose direction is perpendicular to the velocity of the electron. Then

Assertion : A proton and an alpha particle having the same kinetic energy are moving in circular paths in a uniform magnetic field. The radii of their circular paths will be equal.

Reason : Any two charged particles having equal kinetic energies and entering a region of uniform magnetic field $\overrightarrow B $ in a direction perpendicular to $\overrightarrow B $, will describe circular trajectories of equal radii.

At a specific instant emission of radioactive compound is deflected in a magnetic field. The compound can emit

$(i)$ Electrons              $(ii)$ Protons                 $(iii)$ $H{e^{2 + }}$                  $(iv)$ Neutrons

The emission at the instant can be

An electron (mass = $9.0 × $${10^{ - 31}}$ $kg$ and charge =$1.6 \times {10^{ - 19}}$ $coulomb$) is moving in a circular orbit in a magnetic field of $1.0 \times {10^{ - 4}}\,weber/{m^2}.$ Its period of revolution is

A particle moving in a magnetic field increases its velocity, then its radius of the circle

Write equation of Lorentz force.