The voltage between the cathode and the screen of a television set is 22 kV. If we assume a speed of zero for an electron as it leaves the cathode, what is its speed just before it hits the screen?

v= 8.8*10⁷ m/s

Explanation:

Assuming no friction present, the change in electrical potential energy, must be equal in magnitude, to the change in kinetic energy of the electron.The change in the electrical potential energy, can be expressed as follows:

       

The change in kinetic energy, assuming that the electron started from rest, can be written as follows:

       

       ⇒

From the equation above, replacing by ΔK and ΔU, we have:

       

Solving for v: