Coulombs law is the law where you will know the force of between two charge placed in a certain distance the force may be attraction or repletion it will depend upon the nature of two charges. If those two charges are positive then the force will be repulsive and if two are opposite each other positive and negative then the force will be attractive force. Coulombs laws only tells the force between two charges lately Gauss explained the charge flux of the positive charge field. French scientist coulomb explained the law based on given conditions acting between two charges in 1787. The law is called coulomb’s law. At first we need to learn about point charge which will need quite often. Generally we know that a charge attracts another charge or repels another charge. Attraction or repulsion depends upon three terms. These are

(1) the distance between two charges

(2) the amount of two charges

(3) medium between two charges.

**# Point charge: **when the dimension of charged body is very small then the charged body is known as point charge. Small charged bodies are compared according to the distances between then and they are considered as mathematical points.

Now it will become easy to learn coulomb’s law.

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## # Coulomb’s law:

*“The magnitude of attractive or repulsive force between two point charges is directly proportional to the product charges and inversely proportional to the distance of two charges. The force acts as a straight line joining the two charges”*

**#Explanation of coulomb law: **

Let,

Two point charges are q_{1}and q_{2, }

The distance between two point charges is r.

Consider they assert force of magnitude F.

According to coulomb’s law,

_{Here }q_{1}and q_{2 }are constant.

At the time of varying q_{1}, q_{2 }and r. we get from equation (i) and (ii),

Here k is a constant of proportionality. The values of k depend upon the nature of medium and units of q_{1}, q_{2, }r and F. The value of k will depend on the medium nature if the medium is water then it differs from the medium value of air or vacuum. The standard value of k is considered for vacuum.

The force between two charges depends only first of all according to their nature if those two charge are positive the must repulse each other. Question is how the force will be act before you know that you have to tell the quantity of the charge suppose two charge are same quantity and each are +2C the they will repulse with same power. If one positive charge value is higher than another then they will not repel with same force let the two same positive charge value is +10C and +2C then +10C charge has higher magnitude than +2C value larger charge will make force more to the tiny charge. If one charge is the positive and another negative and positive charge magnitude is larger than negative then it be try to take near the negative charge.

## # Coulomb’s Law Problems:

Here are some basic problems of Coulomb’s law by this law we can find the force between two charges attractive or repulsive doesn’t matter. To understand clearly we will see some examples of Coulombs law

**Problem 1: Find the repulsive Coulomb force between two protons in a nucleus of iron?**

**Problem 3: A particle charged with 20C placed 50cm from another 70C charged particle. Find the force between them.**

**Solve:**

Given, q_{1 }= 20C

q _{2 }= 70C

Distance, r = 50cm

= 0.5m

Force, F =?