Problem 11-55 Potential and kinematics in thundercloud - Part 2 - B

Under a particular thundercloud, there is a uniform electric field of \(9.3 \times10^3\; V/m\) upward.

An electron in the field, initially at rest, travels freely for \(3.5 \times 10^{-6} \; m\) before undergoing a collision with a gas molecule. Just before it hits the molecule, what is its speed? Use energy methods.

[Ans. \(1.1 \times 10^5\; m/s\)]

Diagram A showing the field direction and the direction of motion of the electron

Positive charges move with the field and negative charges move against the field.

Correct!

We will take the potential energy of the electron at its original position to be zero. Does it move to a position of:

(A)  lower potential energy?

(B)  higher potential energy (since it can't be negative)?