what magnetic field strength will allow the electron to pass between the plates without being deflected

Complete Question

An electron travels with speed 2.0 X 10^7 m/s between two parallel charged plates. The plates are separated by 2.0 cm and are charged by a 400V battery. What magnetic field strength and direction will allow the electron to pass between the plates without being deflected.?

The value  

Explanation:

From the question we are told that

   The  speed of the electron is  

    The voltage  is  

     The distance of separation is  

Generally the electric field is mathematically represented as

=>    

=>    

Generally for the electron to pass without deflection then

Where is the maximum magnetic force acting on the electron which is mathematically represented as

Since we are considering maximum magnetic field then

=>  

And  

    is the electric force on the electron which is mathematically represented as

Here e is the charge on the electron with the value

=>  

=>      

So

=>    

=>    

what is the question?

this is poiselle's equation from fluid mechanic in physics. mech eng