The Coulomb Constant is a fundamental physical constant that appears in Coulomb’s Law, which describes the electrostatic force between two charged particles. It plays a key role in understanding how charges interact in electric fields and forms the foundation of electrostatics.
Coulomb Constant Definition
The Coulomb Constant, also known as the electrostatic constant, is a proportionality factor in Coulomb’s Law. It relates the magnitude of the electrostatic force between two point charges to the product of their charges and the inverse square of the distance between them.
In simple terms, it tells us how strong the electric force is between two charges in a vacuum.
Coulomb Constant Formula
Coulomb’s Law is mathematically expressed as:
Where:
- F = Electrostatic force between charges (in Newtons, N)
- q1 and q2 = Magnitudes of the two point charges (in Coulombs, C)
- r = Distance between the charges (in meters, m)
- ke = Coulomb constant
Thus, the Coulomb Constant formula is:
Here, ε0 is the permittivity of free space, a physical constant that defines how electric fields behave in a vacuum.
Coulomb Constant Value
The Coulomb Constant value is:
ke=8.9875517923×109 N-m2/C2
This means that if two charges of 1 Coulomb each are placed 1 meter apart in a vacuum, the electrostatic force between them will be approximately 9×109 Newtons — a massive force compared to gravitational forces at the same distance.
Coulomb Constant in a Medium
When charges are placed in a medium other than vacuum, the force between them decreases due to the dielectric constant (εᵣ) of the medium.
The modified form is:
Here,
- εr = Relative permittivity or dielectric constant of the medium.
Therefore, the Coulomb’s Law constant value in any medium is:
This shows that the effective electrostatic constant depends on the surrounding material.
How Was Coulomb’s Constant Determined?
The electrostatic constant was first determined experimentally by Charles-Augustin in the late 18th century. He used a torsion balance apparatus to measure the force between charged spheres. By observing the angle of twist in the balance wire, he quantified the relationship between force, charge, and distance — leading to the discovery of Coulomb’s Law.
With advancements in physics, the value of electrostatic constant was refined using precise measurements of the permittivity of free space (ε₀), which is determined from experiments involving capacitance and electromagnetic wave propagation.
Summary Table: Coulomb Constant Overview
| Aspect | Details |
| Symbol | ke |
| Definition | Proportionality factor relating electrostatic force to charge and distance. |
| Formula | ke = 1 / (4 × π × ε0) |
| Value | 8.9875 × 10⁹ N·m²/C² |
| In Medium (with Dielectric) | k = 1 / (4 × π × ε0 × εr) |
| Determined By | Charles-Augustin de Coulomb (using torsion balance experiment) |
| Unit | Newton meter squared per Coulomb squared (N·m²/C²) |
Conclusion
The electrostatic constant is one of the cornerstones of electrostatics, defining how electric charges interact in space. Its precise value enables accurate calculations in fields like electrical engineering, electronics, and physics. Whether you’re studying electrostatic forces, exploring Coulomb’s Law with dielectric constant, this constant remains essential for understanding the invisible yet powerful forces that govern electric charge interactions.
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