The Unseen Field


Coulomb’s Law

The best to start any blog (I think) is with the basics.


Sadly, not everyone will always understand it the first time. But, with perseverance they or we could understand it through.


—What I Knew—

Regarding the topic on Coulomb’s Law, I had no single clue about  it before. Though I am aware of the basics such as like charges repel and unlike charges attract, and lessons I have learned related to electroscope. Later on, I found out that knowing these greatly helped me in further understanding this.


—What I Learned—


Electric field, an electric property associated with each point in space when charge is present in any form. The magnitude and direction of the electric field are expressed by the value of E, called electric field strength or electric field intensity


Where in…

E = electric field

F = electric force

q = charge in coloumb

The dimensions of electric field are newtons/coulomb, .

We can express the electric force in terms of electric field.

Take note that…

The electric field is normalized electric force. Electric field is the force experienced by a test charge that has a value of +1.

Electric field near an isolated point charge

The electric field direction points straight away from a positive point charge, and straight at a negative point charge.





1. Two unlike charges – attraction.
2. Two like charges – repulsion.
3. A charge and an oppositely charged plate.
4. Two oppositely charged plates.



To start, what is Coulomb’s Law?

Coulomb’s Law quantifies the amount of electrostatic force that two charged object exert on each other, which causes an attraction or repulsion between them.

In other words…

The electric force between charged particles is proportional to the quantity of each of the charges and inversely proportional to the square of the distance between them.



Where in…

  • F is the force exerted between the two charges
  • q1 and q2 are the two charges
  • r is the distance between the two charges
  • coulombs formula or 9 × 10^9 N*m^2/C^2 (k) , also called Coulomb’s constant.




Two point charges are 5.0 m apart. If the charges are 0.20 C and 0.030 C, what is the force between them?




If you’re up to date with the previous blogs, you’d notice that these two formulas are quite similar:

Image result for coulomb's law newtons law

Coulomb’s Law give the electric force while Newton’s Law on Universal Gravitation gives the gravitational force.


  • Attracts
  • Inverse square law
  • Surround objects
  • Cannot be shielded
  • Incredibly weaker



  • Attracts and repels
  • Inverse square law
  • Surround objects
  • Can be shielded
  • Enormously stronger



When we have more than two charges in proximity, the forces between them get more complicated.  The forces, being vectors, just have to be added up.

In other words…

Superposition Principle = The resultant force on a charge is the vector sum of the forces exerted on it by other charges.





CL pr 2

Making a free body diagram basing on the illustration above:

Finding the direction or resultant force:



There are more complicated equations than that. If you want to learn more of it, I recommend this Youtuber/vlogger called: Step-by-Step Science


Here’s the link to his playlist about Coulomb’s Law:




—How I learned—


“A good teacher can inspire hope, ignite the imagination, and instill a love of learning.”

How I learned the most is through the teachings of our very able teacher in Physics, Mr. Lex Supnet *applause*.  He showed us how it’s done were the video clips hadn’t and he helped us master it unlike the video clips would. And so, this quote says it all, Tell me and I forget. Teach me and I remember. Involve me and I learn. So, he didn’t just tolled us what is or how it really is but he teach it to us, like a normal and loving teacher he is. He most especially involved us through the discussions and arguments about what and how he got the correct answer and solution so right.




Like the gravitational law, it exist. Like the gravitational field, it exist. But, how about you and your ex? Did it exist? Maybe it’s a no or just a big maybe but we’ve gone through several challenges through out our life were it seemed like it would never end but for the people who made that law, who didn’t slept for many days, and for those that believed it would be possible but suddenly  gave up and lost hope. For you and your ex? did you go through all of that just to keep her/him? Or maybe you just gave up like the rest are and just left without a word, it hurts right?! Not to be noticed, not to be talked to, and just being ignored like an old theory that has been left but unfortunately for you the old theory will be remembered, will be praised again, and most especially it would be valued again. How about you? Do you think your past relations would be remembered, praised, and valued once more? I think not because people today, people like you, us are just not worth it to be remembered, to praised, and to be valued once more.

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