Electric Force: Difference between revisions
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== Claimed by Azan Khan — Fall 2025 == | |||
This page | 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 == | ||
The | * 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|400px|thumb|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) | |||
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.
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)