The electrostatic force between the metal plates of an isolated parallel plate capacitor C having a charge Q and area A, is

An electron falls from rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is

A toy car with charge q moves on a frictionless horizontal plane surface under the influence of a uniform electric field $$\overrightarrow E $$ . Due to the force q$$\overrightarrow E $$ , its velocity increases from 0 to 6 m s^–1 in one second duration. At that instant the direction of the field is reversed. The car continues to move for two more seconds under the influence of this field. The average velocity and the average speed of the toy car between 0 to 3 seconds are respectively

A capacitor is charged by a battery. The battery is removed and another identical unchanged capacitor is connected in parallel. The total electrostatic energy of resulting system