A narrow electron beam passes undeviated through an electric field `E = 3 xx 10^(4) "volt"//m` and an overlapping magnetic field `B = 2 xx 10^(-3) Weber//m^(2)`. If electric field and magnetic field are mutually perpendicular. The speed of the electron is

Options

A. `60 m//s`
B. `10.3 xx 10^(7) m//s`
C. `1.5 xx 10^(7)m//s`
D. `0.67 xx 10^(7) m//s`

Answer

B

Explanation

If elctron beam passes undeviated then magnetic force should nalance electirc force
`v = (E)/(B) = (3 xx 10^(4))/(2 xx 10^(-3)) = 1.5 xx 10^(7) m//sec`.