An electron in a TV is accelerated toward the screen. The potential between the back of the tube and the screen is 22,000 V (which is why it is a VERY good idea not to play around TV picture tubes). How much kinetic energy does the electron lose when it strikes the TV screen?

The kinetic energy lost by the electron ΔK.E is 3.5244 × 10⁻¹⁵ J

Explanation:

Here we have;

Change in electric potential, ΔV, of the screen = 25000 V

The energy gained by the electron can be derived from the relation of change in electrical potential energy, ΔEPE, as follows;

ΔEPE = -Charge, q × ΔV

Therefore, since charge, q = -1.602 × 10⁻¹⁹ C we have;

ΔEPE = -(-1.602 × 10⁻¹⁹ C) × 25,000 V = 3.5244 × 10⁻¹⁵ C·V =

Also, since the electron is accelerated to the screen by the electrical potential energy, we have;

From the principle of conservation of energy in a given system;

The change in potential energy, ΔEPE of the electrons = Change in kinetic energy, ΔK.E, of the electrons3.5244 × 10⁻¹⁵ J

Where:

m = Mass of the electron = 9.11 × 10⁻³¹ kg

= Initial velocity of the electrons = 0 m/s (electrons at rest)

= Final velocity of the electrons

Hence;

The kinetic energy lost by the electron ΔK.E = ΔEPE = 3.5244 × 10⁻¹⁵ J.