Question

An electron is released form rest in a region of space where a uniform electric field is present. Joanna claims that its kinetic and potential energies both increase as it moves from its initial position to its final position. Sonya claims that they both decrease. Which one, if either, is correct

Answer 1

Answer:

reviewing the opinion of the two students we see that neither is right, since when the kinetic energy increases the potential energy decreases by the same value

Explanation:

For this exercise we must use the law of conservation of energy.

Starting point. Resting electron

        Em₀ = U = eV

the potential difference and the electric field are related

         V = - E d

Final point. When leaving the electric field

           $Em_{f}$ = K = ½ m v²

           Em₀ = Em_{f}

           e E d = ½ m v²

From this expression we see that when an electron moves from the initial point to the final point, the potential energy must decrease, for the total energy to be constant.

When reviewing the opinion of the two students we see that neither is right, since when the kinetic energy increases the potential energy decreases by the same value