Question

Which one of the following statements is true concerning the work done by an external force in moving an electron at constant speed between two points in an electrostatic field?

A) The work done is always zero joules.
B) The work done is always positive.
C) The work done only depends on the speed of the electron.
D) The work done depends on the total distance covered.
E) The work done depends only on the displacement of the electron

Answer 1

The true statement concerning the work done by an external force in moving an electron at constant speed between two points in an electrostatic field is E) The work done depends only on the displacement of the electron.

To explain this, consider the following steps:

1. The work done by an external force is given by the equation W = F × d × cosθ, where W is the work done, F is the force applied, d is the displacement, and θ is the angle between the force and displacement vectors.
2. When moving an electron at constant speed in an electrostatic field, the external force should be equal in magnitude but opposite in direction to the electrostatic force acting on the electron.
3. This means that the angle θ between the force and displacement vectors will be 0 degrees, and cosθ = 1.
4. Therefore, the work done (W) depends only on the product of the force applied (F) and the displacement (d).

So, the correct answer is E) The work done depends only on the displacement of the electron.