The Attraction and Repulsion of Charged Bodies

Charged bodies exert forces on each other due to fundamental principles of electromagnetism, specifically described by Coulomb's law and the concept of electric fields. This article explores how charged particles interact, the underlying theories, and the practical applications of these principles.

Key Concepts

Coulomb's Law

Coulomb's law describes the electrostatic interactions between point charges. According to this law, the force F between two point charges q1 and q2 is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance r between them:

F k frac{q_1 q_2}{r^2}

Here, k is Coulomb's constant, approximately equal to 8.99 times 10^9 N , m^2/C^2. The force is attractive if the charges are of opposite signs (one positive and one negative) and repulsive if they are of the same sign (both positive or both negative).

Electric Fields

A charged body creates an electric field in the surrounding space. The electric field E at a distance r from a point charge q is given by:

E k frac{q}{r^2}

When another charge is placed in this electric field, it experiences a force F given by:

F qE

Thus, the electric field of a charged body exerts a force on other charges placed within that field.

Interactions

When two charged bodies are brought close to each other, they interact through their electric fields. Depending on their charges, this interaction results in a force of attraction or repulsion. A positively charged object will attract a negatively charged object, whereas oppositely charged objects will exert an attractive influence on each other. This phenomenon can be seen in the macro world.

For example, pieces of thin plastic or shrink wrap have an impish tendency to 'stick' to our body or pieces of furniture due to static electricity. Similarly, ions, which have a positive or negative charge, attract each other. This is analogous to magnets, where the north pole of one magnet attracts the south pole of another. However, magnetism is a different force that acts on a macro scale, which we can detect easily with our senses.

Back in high school, we were taught that the attraction of atoms with dipole nature or molecules with dipole nature was due to the loss of one or more electrons, causing an imbalance in the atom or molecule. One side then had a positive charge, and the other side had a negative charge. The forces that attract positive to negative charges are called Van der Waals forces, and they are much weaker than covalent bonds, which are formed when two atoms share a common electron and are 'hooked' together very tightly.

Summary

Charged bodies exert forces on each other due to the interaction of their electric fields and the principles outlined in Coulomb's law. This fundamental interaction is a cornerstone of electromagnetism and explains a wide range of phenomena, from static electricity to the behavior of charged particles in electric fields.

The question of why charged bodies exert forces on each other touches on the deeper and critical aspects of physics. While science can explain 'how' these interactions occur, the 'why' of these interactions remains a fundamental mystery. Even Einstein's General Theory of Relativity, which includes gravity, does not provide a truly explainable base cause for gravitational attraction. Static electricity and Van der Waals forces offer glimpses into these interactions, but a more complete explanation of the 'why' remains a challenge for scientists and physicists.