EMT: 2nd week part 2 Coulomb's law + Electric Field Intensity of Point charges

Hey there~

In 2nd week, we also learn about COULOMB's law!

Here is the summary and the example.

 COULOMB's law states that:

  The force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance of separation.

To have a better understanding on the formula, consider the force between charges is affected by 3 factors:

1) Force is directly proportional to the product of 2 charges

2) Force is inversely proportional to the square of R (radius).

3) the medium, which is free space is most of the case (8.854 x 10-12)

Here you go~ the formula:

 Superposition method can be used to find the total forces act on a single charge if multiple forces present.

  

Theory part finished! Let's go to the example!

Example:

Point charges 5 nC and -2 nC are located at (2,0, 4) and (-3,0, 5), respectively.

(a) Determine the force on a 1-nC point charge located at (1, -3, 7).

(b) Find the electric field E at (1, -3, 7)

Solution:

a)

Remember that there are 4 types of sources in electrostatic? This is the type 1 which is point charge problem.

#To solve this kind of question, it is important to draw first, however the position of the charges aren't necessary to be according to the real position.

b) To calculate the electric field, E = F/Q. (Q is the charge that forces been acted upon.)

Please note that the unit of electric field can be volt/meter or Newton/Coulomb. Either ways will do it~ :) 

Hope you guys can understand the concept of Coulomb's law and the example! Hehe :)

Regards,

Daniel