Question

The ratio of magnetic force to electric force on a charged particle getting undeflected in a region where there are mutually perpendicular electric and magnetic fields is

Answer 1

Let $F_m$ and $F_e$ be magnetic force and electric force respectively.
The charge particle went undeflected through the region of electric and magnetic fields. Hence net force acting on the particle must be zero.
$⟹F_e=F_m$
$⟹\frac{F_e}{F_m}=1$