Question 1

What is an electric field?

Accepted Answer

An electric field is a region around a charged object where other charges experience a force. The field points away from positive charges and toward negative charges. Its strength at any point tells you the force per unit charge that a small positive test charge would experience there: E = F/q.

Question 2

What is Coulomb's constant?

Accepted Answer

Coulomb's constant k = 8.9875 × 10⁹ N·m²/C² (often approximated as 9 × 10⁹) determines the strength of electrostatic interactions. It is related to the permittivity of free space by k = 1/(4πε₀). This constant appears in Coulomb's law and electric field equations for point charges.

Question 3

How does the electric field relate to electric potential?

Accepted Answer

The electric potential V = kQ/r is the potential energy per unit charge. The electric field is the negative gradient of the potential: E = -dV/dr. For a point charge, E = kQ/r² while V = kQ/r. The field tells you about forces, while potential tells you about energy.

Question 4

Why does the electric field follow an inverse-square law?

Accepted Answer

The electric field decreases as 1/r² because the field lines spread out over the surface of a sphere. As distance doubles, the same number of field lines passes through four times the area (since sphere area = 4πr²), so the field strength drops to one quarter. This is the same geometric reason gravity follows an inverse-square law.

Electric Field Calculator (E = kQ/r²)

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