Adiode vacuum tube consists of a cathode and an anode spaced 5-mm apart. if 300 v are applied across the plates. what is the velocity of an electron midway between the electrodes and at the instant of striking the plate, if the electrons are emitted from the cathode with zero velocity?

Velocity of the electron mid way = v = 6.47×10⁶ m/s  

Explanation:

Electric potential varies with distance as

At a distance 5 mm , the constant C is evaluated.

C =

    =

     = 3.50×10⁵  

Now at the mid point, x = 2.5 mm = 0.0025 m

Potential = V' =

                      =

                      = 119 V

Kinetic energy per unit charge is equal to the electric potential.

or 0.5 m v^2 = V' q

Here m is the mass of the electron and q is the charge of the electron.

m= 9.1×10⁻³¹ kg

q = 1.6×10⁻¹⁹ coulombs

⇒

⇒

⇒ v = 6.47×10⁶ m/s

⇒ Velocity of the electron mid way = v = 6.47×10⁶ m/s    

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)