Fundamental concepts of chemistry: Electrostatic force of attraction/Coulomb’s force

This force is named after a French scientist “Charles Augustin Coulomb’, who defines about this force for the first time in 1785, consequently, this is also called Coulomb’s force.

1. Definition:

These forces are produced through electric charge of the particles and exist between charged particles. Electrostatic forces can be attractive or repulsive, and are liable for the stability of an atom. These are the main binding forces among ionic compounds that combine the ionic species in ionic compounds. These forces are among the four fundamental forces that exist between nuclear particles, allied with electromagnetic force.

2. Properties:

1.      Electrostatic forces show some particular properties which are described as follows

2.      Similar charges are repelled by each other, while dissimilar ones show the opposite behavior as they strongly attract each other.   

3.      Magnitude of these forces directly depends on product of electric charges

4.      The distance among these charges inversely affects the strength of these forces

5.      These forces exist between the axis line joining these charges  

3. Principle governing electrostatic forces:

The Coulomb’s law of electrostatic forces of attraction describes some specific properties of these forces at rest. This law demonstrates the dependence of these forces on distance and magnitude of two charges and usually applied on point charges. According to this law “same charges (a pair of positive-positive or negative-negative) always repel each other when present in vicinity, while the opposite charges (a pair of positive-negative) on the other hand attract each other’. For instance, a proton will repel the second proton that is situated in its proximity, at the same time a cation will repel the same entity with similar charge. On the other hand, paradoxically to proton-proton repulsion, a proton will always attract electron due to divergent charge present on it, and same is the case with cation and anion that attract each other. As electrons attract the protons from outside the nucleus, nevertheless, these protons never jump out of nucleus due to strong nuclear forces present inside the nucleus that do not permit these particles to stick with outside electrons.

The strength of coulomb’s forces, weather attractive or repulsive, can be calculated through Coulomb’s law using the following equation

       


Where

F = Electrostatic force

K = Proportionality constant/Coulomb’s constant

q1 & q2 = electric charges

r = distance among centers of these charges

According to equation 1, the magnitude of electric charges is directly proportional to the electrostatic force F, while this force is inversely proportional to the distance between these two entities. At a condition where distance between two charges reaches to infinity, the value of F becomes zero and the electrostatic forces do not exist among those particles. The values of point charges (q1 & q2) can have one of the positive or negative sign. When the force is attractive in case of two opposite charges, it possesses a negative charge. In contrast, the two same charges assign a positive charge to it in case of repulsive forces. Figure 1 shows the schematic diagram of coulomb’s law of electrostatic interactions.


Figure. 1 Schematic diagram of repulsive and attractive electrostatic forces 

4. Existence of electrostatic forces in daily chores:

Ø  The lighting phenomenon of clouds is produced by the resistance of opposite charges with each other, and these charges strike on ground to get neutralize with a blast.

Ø  The stickiness of small pieces of paper with comb just after combing is the most common example of production of electrostatic forces.

Ø  Silk and wool fabric usually clings to our body owing to rubbing of charged particles exist in this stuff.



       


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