Coulomb's Law. Physics. Class 10. Physical Science.
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Today we are going to learn the very basic rule of electromagnetism. If you don't know that particular rule, you will not be able to understand the other topics of electromagnetism. In the year 1785, the French physicist Charles Augustine de Coulomb discovered this famous rule. That's why it's called the Coulomb's Law.
The statement of the formula is.
For The first formula.
Opposite electrical charges attract each other. And identical charges repel.
The second formula is.
The magnitude of this attractive or repulsive force is proportional to the product of the elemental charges, and inversely proportional to the Square of the distance between them.
Suppose there are two charges. One is positive, the other is negative. Then they will attract each other. Because the opposite charges attract. As a result of these attraction, they tend to come to closer and closer.
If both charges are positive, they will repel each other. And will move away from each other.
In the same way, if we place two negative charges at a closer distance, they also repel each other. And will move away further and further.
Now let's come to the second formula.
If the amount of charge in the first particle be q1. And that of the second particle be q2. Also, the distance between them be r. Then the amount of active force between them is proportional to the product of q1 and q2. When the value of r remains unchanged.
That is, the force or F varies to q1 into q2. When r is constant.
Again if the magnitude of the product q1q2 ​​are the same, F varies one by r square.
Using the compound theorem of variation.
F varies to q1 into q2 by r square. When q1, q2, and r, are variables.
Or, F is equal to k into q1 into q2 by r square.
Where k is a constant number. The values ​​of k depends on the properties of materials in which the charged particles are staying. In S,I, System of unit the expression for k is one by four pi into Epsilon Zero INTO EPSILON R.
Where, Epsilon Zero is a universal constant, better known as the permittivity of free space. Whose worldwide accepted value is 8.85 into Ten to the power minus twelve farad per meter.
Epsilon R, is called as the relative permittivity of a medium. For media like air or free space, it assumes a value of 1.
Check out the Epsilon R values ​​for some other media.
Hope, this video has been able to generate a clear concept in you.
Will come back in our next video.
Thanks for watching the video till the end.