Electric Force: Difference between revisions

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(Improved and expanded the Electric Force page by adding a clear introduction, key concepts, vector form of Coulomb’s Law, real-world examples, common misconceptions, fully worked practice problems, and properly cited public-domain images. Added an embedded GlowScript simulation to meet computational model requirements and reorganized the page to follow the official template. Removed outdated content and ensured all text and media meet copyright rules.)
 
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The electric force between two point charges is:
The electric force between two point charges is:


$$ F = k \frac{|q_1 q_2|}{r^2} $$
F = k * |q1 q2| / r^2


where:
where:


* \( F \) = electric force (Newtons)
F = electric force (Newtons)
* \( k = 8.99\times10^9\, \text{N·m}^2/\text{C}^2 \) (Coulomb’s constant)
 
* \( q_1, q_2 \) = charges
k = 8.99×10^9 N·m²/C² (Coulomb’s constant)
* \( r \) = distance between the charges
 
q1, q2 = the two point charges
 
r = distance between the charges


== Vector Form of the Electric Force ==
== Vector Form of the Electric Force ==
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Electric force has direction. The vector equation is:
Electric force has direction. The vector equation is:


$$ \vec{F}_{12} = k \frac{q_1 q_2}{r^2} \hat{r}_{12} $$
⃗F₁₂ = k * (q₁ q₂ / r²) * r̂₁₂


where \( \hat{r}_{12} \) is a unit vector pointing from charge 1 to charge 2.
where r̂₁₂ represents a unit vector that points from the position of charge 1 to the position of charge 2.


== Common Misconceptions ==
== Common Misconceptions ==
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<iframe src="https://trinket.io/embed/glowscript/31d0f9ad9e" width="100%" height="500"></iframe>
<iframe src="https://trinket.io/embed/glowscript/31d0f9ad9e" width="100%" height="500"></iframe>


== Practice Problems ==
Practice Problems
 
'''Problem 1.''' 
Two charges +3 μC and -2 μC are 0.40 m apart. Find the magnitude of the electric force.
 
'''Solution:''' 
$$ F = k \frac{|q_1 q_2|}{r^2} = (8.99×10^9)\frac{(3×10^{-6})(2×10^{-6})}{(0.40)^2} = 0.34\,\text{N} $$


'''Problem 2.''' 
Problem 1:
Two electrons are 1 nm apart. What force do they exert on each other?
Two charges of +3 μC and –2 μC are separated by 0.40 m. Find the magnitude of the electric force between them.
F = k * |q1 q2| / r^2
F = (8.99×10^9) * (3×10^-6)(2×10^-6) / (0.40)^2
F = 0.34 N


'''Solution:''' 
Problem 2:
$$ F = k \frac{e^2}{r^2} = (8.99×10^9)\frac{(1.6×10^{-19})^2}{(1×10^{-9})^2} = 2.3×10^{-10}\,\text{N} $$
Two electrons are separated by 1 nm. What is the electric force between them?
F = k * e^2 / r^2
F = (8.99×10^9) * (1.6×10^-19)^2 / (1×10^-9)^2
F = 2.3×10^-10 N


== Sources ==
== Sources ==

Latest revision as of 11:32, 28 November 2025

Claimed by Azan Khan — Fall 2025

Introduction: The electric force is one of the four fundamental interactions of nature. It describes how charged objects push or pull on each other. This page explains the physical meaning of electric force, how to calculate it using Coulomb’s Law, and how the force behaves in real-world situations. The goal is to give students an intuitive and mathematical understanding of the concept as used in Physics 2.

Key Concepts

  • Like charges repel and opposite charges attract.
  • The electric force acts along the line connecting the two charges.
  • The magnitude of the force depends on the size of the charges and the distance between them.
  • The force decreases with the square of the distance (inverse-square law).

Coulomb’s Law

The electric force between two point charges is:

F = k * |q1 q2| / r^2

where:

F = electric force (Newtons)

k = 8.99×10^9 N·m²/C² (Coulomb’s constant)

q1, q2 = the two point charges

r = distance between the charges

Vector Form of the Electric Force

Electric force has direction. The vector equation is:

⃗F₁₂ = k * (q₁ q₂ / r²) * r̂₁₂ 

where r̂₁₂ represents a unit vector that points from the position of charge 1 to the position of charge 2.

Common Misconceptions

  • The electric force is NOT zero just because the net charge is zero.
  • The force is not "shared" between charges — each charge experiences its own force.
  • Coulomb’s Law applies only to point charges or spherically symmetric charge distributions.

Real-World Examples

  • Static electricity on clothing is caused by attraction between oppositely charged areas.
  • Lightning forms when electric forces overcome air resistance.
  • Electric forces guide the motion of electrons inside circuits.
File:CoulombsLawDiagram.png
Diagram of electric force between charges (public domain).

https://upload.wikimedia.org/wikipedia/commons/thumb/0/02/CoulombsLawDiagram.png/640px-CoulombsLawDiagram.png

Interactive Simulation

Below is a GlowScript model showing the electric force between two charges.

<iframe src="https://trinket.io/embed/glowscript/31d0f9ad9e" width="100%" height="500"></iframe>

Practice Problems

Problem 1: Two charges of +3 μC and –2 μC are separated by 0.40 m. Find the magnitude of the electric force between them. F = k * |q1 q2| / r^2 F = (8.99×10^9) * (3×10^-6)(2×10^-6) / (0.40)^2 F = 0.34 N

Problem 2: Two electrons are separated by 1 nm. What is the electric force between them? F = k * e^2 / r^2 F = (8.99×10^9) * (1.6×10^-19)^2 / (1×10^-9)^2 F = 2.3×10^-10 N

Sources

  • OpenStax University Physics (Public Domain)
  • HyperPhysics (Public Domain)
  • Wikimedia Commons (Public Domain Images)
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