Physics Lesson 14.3.3 - Electrostatic Constants

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Welcome to our Physics lesson on Electrostatic Constants, this is the third lesson of our suite of physics lessons covering the topic of Electric Field, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.

Electrostatic Constants

In the previous tutorial, we explained that the electrostatic constant k = 8.988 × 10⁹ N × m₂/C² found experimentally (and known as Coulomb's constant), is used to turn the proportion between the two sides of Coulomb's Law into equality. However, the Coulomb's constant k is the simplified version of electrostatic constant (as its power is positive). In fact, there is another quantity, which is recognized as the "true" electrostatic constant. It is denoted by ϵ⁰ and its relation with the Coulomb's constant k is

ϵ₀ = 1/4π × k

When substituting the known values, we obtain for ϵ⁰

ϵ₀ = 1/4 × 3.14 × 8.988 × 10⁹ N × m²/C²
= 8.85 × 10^-12 C²/N × m²

The constant ϵ⁰ is more common in electricity-related formulae. This is the reason why it is more important than the Coulomb's constant k.

We can therefore write for the formulae of electrostatic force and electrostatic field in terms of ϵ⁰:

F = 1/4πϵ₀ × Q × Q₀/r²

and

E = 1/4πϵ₀ × Q/r²

You have reached the end of Physics lesson 14.3.3 Electrostatic Constants. There are 6 lessons in this physics tutorial covering Electric Field, you can access all the lessons from this tutorial below.

More Electric Field Lessons and Learning Resources

Electrostatics Learning Material
Tutorial ID	Physics Tutorial Title	Revision Notes	Revision Questions
14.3	Electric Field
Lesson ID	Physics Lesson Title	Lesson	Video Lesson
14.3.1	What Is Electric Field? Similarities between Gravitational and Electric Field
14.3.2	Electric Field Lines
14.3.3	Electrostatic Constants
14.3.4	The Superposition Principle
14.3.5	Electric Field on a Charged Sphere
14.3.6	Conductors in an Electric Field

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