Electric field inside conductors is a core Electrostatics concept in Physics. This guide explains what it is, walks through a fully worked example, and lists the key equations you need — with a short quiz to test yourself.

Key equations and worked example

Two 5 µC charges, opposite signs, 10 cm apart: F = k·q₁q₂/r² = (9×10⁹)(5×10⁻⁶)²/(0.1)² ≈ 22.5 N attractive. Flip one sign and the same 22.5 N becomes repulsive — the field lines redraw themselves instantly. The field midway between opposite charges is E ≈ 2kq/r², pointing from + to −.

• <code>Coulomb&#39;s law: F = k·q₁·q₂ / r²</code>
• <code>Electric field: E = F/q = k·Q / r²</code>
• <code>Potential: V = k·Q / r</code>
• <code>Field at conductor surface: E = σ/ε₀</code>

Electric field inside conductors in detail

Electric field inside conductors is one of the central ideas in Electrostatics, and it appears in Physics curricula under Gauss&#39;s law and applications. It is worth learning deeply because it connects to so many other topics in this section.

Static charges exert Coulomb forces along the line joining them — like charges repel, opposites attract. The electric field E = F/q maps the force a test charge would feel; field lines leave positive charges and enter negative ones, never crossing. Conductors in equilibrium carry charge only on their surface, with zero field inside.

For exams, the pattern is predictable: first a definition or statement of the result, then a direct numerical application of one of the equations above, then a "why" question — why the formula takes that form, or what changes when a variable is doubled or halved. The worked example and quiz below cover exactly that progression.

Quick self-check:

• Q: Doubling the distance between two charges changes the force by what factor?<br />A: It drops to one-quarter — Coulomb&#39;s law is inverse-square.
• Q: Which way do electric field lines point?<br />A: Away from positive charges and toward negative charges; they never cross.
• Q: Why is the electric field zero inside a charged hollow conductor?<br />A: Free charges repel to the outer surface; Gauss&#39;s law then gives zero enclosed charge, so zero field inside.