# Finding the Initial Charge on a Sphere Based on Coulomb's Law

• ppdjoy
In summary, two identical metal spheres with initial charge q1 > 0 and |q1| > |q2| attract each other with a force of 75.6 mN. After being brought into contact, the spheres have the same final charge q, and when moved 3.33 m apart, they repel each other with a force of 8.316 mN. Using the Coulomb constant, the initial charge q1 on the first sphere can be calculated.

## Homework Statement

Two identical small metal spheres with q1 > 0 & |q1| > |q2| attract each other with a force of magnitude 75.6 mN, as shown in the http://localhostr.com/files/ffac57/1.JPG" [Broken].

The spheres are then brought together until they are touching. At this point, the spheres are in electrical contact so that the charges can move from one sphere to the other until both spheres have the same final charge, q.
http://localhostr.com/files/62ffcf/2.JPG" [Broken]

After the charges on the spheres have come to equilibrium, the spheres are moved so that they are again 3.33 m apart. Now the spheres repel each other with a force of magnitude 8.316 mN.
http://localhostr.com/files/6911b9/3.JPG" [Broken]

The Coulomb constant is 8.98755*10^9 N*m^2/C^2

What is the initial charge q1 on the first sphere?

F = Ke q1*q2/r2

## The Attempt at a Solution

I was thinking that using this formula, I can get to q1. But apparently, it's not leading me anywhere.

Can anyone tell me if I'm using the right formula or not? If not, then which formula do I use? I didn't understand this material in class very well, so, if someone kindly explains how to do this problem, I'll really appreciate it.

Thanks

Last edited by a moderator:
Since they are attracting initially, q1 and q2 must have opposite charges.
When they are brought in contact, they will have the equal charges of the same sign, and the charge in each sphere will be ...?

## What is Coulomb's electricity?

Coulomb's electricity refers to the concept of electric charge and the forces that act between charged particles. It was first described by French physicist Charles-Augustin de Coulomb in the late 18th century.

## What is Coulomb's law?

Coulomb's law states that the force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. It is represented by the equation F = kq1q2/r2, where k is the proportionality constant, q1 and q2 are the charges, and r is the distance between them.

## How is Coulomb's law related to electric fields?

Coulomb's law is used to calculate the magnitude and direction of the electric field created by a single point charge. The electric field is a vector quantity that describes the force that a charged particle would experience at any given point in space.

## What is the difference between Coulomb's law and Gauss's law?

While Coulomb's law is used to calculate the force between two charged particles, Gauss's law relates the electric field to the distribution of charges in a closed surface. Gauss's law is often used to simplify calculations involving complex charge distributions.

## How is Coulomb's law used in everyday life?

Coulomb's law has many practical applications, such as in the design of electronic devices, the behavior of lightning, and the functioning of batteries. It is also used in industries such as telecommunications, power generation, and medical technology.