The document discusses the physics of electric force between charged plates. It defines electric force as the attraction or repulsion between two charged particles that is directly related to their charges. The magnitude of the electric field between two metal plates with different applied voltages can be calculated using the charges, surface area of the plates, and the vacuum dielectric constant. The document then describes an experiment to measure the electric force between plates using a laser and balance, taking measurements of initial and final laser positions and distances to calculate the separation between the charged plates.