Two parallel infinite line charges with linear charge densities +$$\lambda $$ C/m and -$$\lambda $$ C/m are placed at a distance of 2R in free space. What is the electric field mid-way between the two line charges?

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

Suppose the charge of a proton and an electron differ slightly. One of them is $$-$$e, the other is (e + $$\Delta $$e). If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance d (musch greater than atomic size) apart is zero, then $$\Delta $$e is of the order of
[Given : mass of hydrogen m_h = 1.67 $$ \times $$ 10$$-$$²⁷ kg]