# How Can I Determine the Value of Charges in Coulomb's Law?

• Josh225
In summary: LawIn summary, Coulomb's Law is a formula that relates the force, F, between two charges, q1 and q2, and the distance between them, r. If q1 and q2 are unknown, the formula can be used to find q1 by multiplying F by r^2.
Josh225
Hello, I am pretty new to physics. I have no formal education on physics, and I have been studying it on my own out of curiosity and fascination. Please correct me if anything that I say is wrong and assume I know nothing. Math is also not my strongest skill, but I am trying to become better.

For the past couple of days, I have been working with Coulomb's Law. From my understanding the formula used is : (k) q1q2/r^2. I feel pretty comfortable with the formula and I have been doing some practice problems and getting them correct. In all of the questions though, q1 and q2 are given to me. I would like to know how to find the value of "q" without it being given to me.

If I were to construct my own experiment and put 2 charges at a certain distance from each other, how would I go about finding the value of the charges?

Thanks!

##F=\frac{k_E \cdot q_1 \cdot q_2}{r^2}⇔q_1=\frac{F\cdot r^2}{k_E\cdot q_2}##

Thanks! What is that called so I can look more into it?

Josh225 said:
Thanki! What is that called so I can look more into it?
I do not think this equation ##q_1=\frac{F\cdot r^2}{k_E\cdot q_2}## has any name. Just another form of Coulomb law.

Josh225 said:
If I were to construct my own experiment and put 2 charges at a certain distance from each other, how would I go about finding the value of the charges?

From Coulomb's Law, if you measure the separation of the charges, r, and the force on either one, you could only find the product of the two charges, q1q2. If you knew the value of one of the charges then you could use the above formula to find the other. Also, if the two charges were equal, q1 = q2 = q, then Coulomb's Law would give you q^2 so you could calculate q.

How do I measure the force of the individual charge though?

Josh225 said:
How do I measure the force of the individual charge though?
##F_{coulomb}=F_{net}-F_{other}##
you can measure net force with Newton meter.
Or consider that Newton II law ##F_{net}=a*m## and measure acceleration and mass.

olgerm said:
Or consider that Newton II law ##F_{net}=a*m## and measure acceleration and mass.

This would get complicated if there is acceleration, i.e. the charges are not at rest, since then the separation distance, r, would be changing and the force would not be constant.

One possible experiment would be to suspend two charged objects on strings. The Coulomb force would cause the objects to attract or repel, depending on the charges, and the strings would deviate from the vertical. Knowing the mass of the objects and measuring the angle of deviation from the vertical, the Coulomb force can be calculated.

Josh225
As far are the 2 charged objects are concerned, what material would be the best to use? My knowledge on the subject is extremely limited.

Ben Franklin as my Lab Partner (Robert Morse)

http://mysite.du.edu/~jcalvert/phys/elechome.htm
http://mysite.du.edu/~jcalvert/phys/elechome.htm#Coul

## 1. What is Coulomb's Law?

Coulomb's Law is a fundamental law of physics that states the force of attraction or repulsion between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

## 2. How is Coulomb's Law used in science?

Coulomb's Law is used to calculate the force between two charged particles, such as protons and electrons. It is also used to understand the behavior of electric fields and the movement of charged particles in electric fields.

## 3. What units are used in Coulomb's Law?

The units used in Coulomb's Law are Newtons (N) for force, Coulombs (C) for charge, and meters (m) for distance. The equation can also be written in terms of electric field (N/C) and electric potential (V).

## 4. How does distance affect the force in Coulomb's Law?

According to Coulomb's Law, the force between two charged particles decreases as the distance between them increases. This is because the force is inversely proportional to the square of the distance, meaning that as the distance doubles, the force decreases by a factor of four.

## 5. Can Coulomb's Law be applied to all types of charged particles?

Yes, Coulomb's Law can be applied to all types of charged particles, regardless of their size or composition. It is a universal law that governs the behavior of electrically charged objects in the universe.

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