Determine the magnitude of the electrical force between these ions if the membrane thickness is 0.80 * 10-9 m. ignore the effect of the material in which the ions are located.

In Coulomb's law the force between the charged objects depends on the distance between them which is inversely proportional to the force and the charge of the objects which is directly proportional to the force with proportional constant K.

Because q₂ is near to another charged object q₁, then, it will experience an electric force exerted by q₁.

F₁₂ = K |q₁| |q₂|/r²

= K (|-e|) (|+e|) / r²

= (9.0 x 10⁹ N. m²/C²) x (1.6 x 10⁻¹⁹ C) x (1.6 x 10⁻¹⁹ C) / (0.80 x 10⁻⁹) ²

= 3.6 x 10⁻¹⁰ N

Force F₁₂ = F₂₁

Because the two charged objects have different signs, then, the force between them will be an attractive force.