An electron beam is allowed to pass normally through megnetic and electric fields which are mutually perpendicular. When the magnetic filed inductionand electric field strength are `0.0004Wbm^(-2)and 3000Vm^(-1)`respectively the beam suffers no deflection .Then the velocity of electron is

Options

A. `7.5xx10^(6)ms^(-1)`
B. `7.5xx10^(4)ms^(-1)`
C. `7.5xx10^(2)ms^(-1)`
D. `1.2xx10^(6)ms^(-1)`

Answer

A

Explanation

Magnetic field ,`B=0.0004Wbm^(-2)=4xx10^(-4)``Wbm^(2)`
Electric field ,`E=3000Vm^(-1)`
The expression for the velocity of the electron is given as,
`V=(E)/(B)`
`=(3000)/(4xx10^(-4))`
`V=7.5xx10^(6)ms^(-1)`