Coulombic Repulsion

Coulomb's law states that: 

• The magnitude of the electrostatic force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distance between them. 

• The force is along the straight line joining them.

•  If the particles are both positively or negatively charged, the force is repulsive; if they are of opposite charge, it is attractive.

• The law was first published in 1784 by French physicist Charles Augustin de Coulomb and was essential to the development of the theory of electromagnetism. It is analogous to Isaac Newton's inverse-square law of universal gravitation.

Task: Watch Khan Academy's video on Coulomb's Law and answer the following questions:

1. The nucleus in an iron atom has a radius of about 4.0 x 10-15 m and contains 26 protons.

   • What is the magnitude of the repulsive electrostatic force between two of the protons that are separated by 4.0 x 10-15 m?

   • What is the magnitude of the gravitational force between those same two protons?

   • Data: Charge of proton = 1.602 x 10-19 C; Mass of proton = 1.67 x 10-27 kg.

   • Data: Coulomb Law Constant k = 8.99 x 109 N m2/C2 

   • Data: Gravitational Constant G = 6.67 x 10-11 N m2/kg2

2. Determine the magnitude and the direction of the electric force of the proton on the electron in a hydrogen atom. [Check your answer here]