---
title: "Conductors, Shielding and Surface Charge"
description: "In electrostatic equilibrium the field inside a conductor is zero, all excess charge sits on the surface, and the field just outside is perpendicular to it. A closed conducting shell shields whatever "
canonical: https://lightmysky.com/learn/science/conductors-shielding-and-surface-charge-mt_2zmzTE-dgL
source: https://lightmysky.com/learn/science/conductors-shielding-and-surface-charge-mt_2zmzTE-dgL.md
retrieved: 2026-09-12
---

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# Conductors, Shielding and Surface Charge

In electrostatic equilibrium the field inside a conductor is zero, all excess charge sits on the surface, and the field just outside is perpendicular to it. A closed conducting shell shields whatever is inside it.

Subject: Science · Area: Electricity & Magnetism · Ages 18 to 20
Page: https://lightmysky.com/learn/science/conductors-shielding-and-surface-charge-mt_2zmzTE-dgL

## Ready when they can

- Argues from equilibrium that the field inside conducting material must vanish
- Locates the induced charge on the inner and outer surfaces of a shell with a charge inside
- Explains why a car body protects its occupants during a lightning strike

## Lesson: Quiet inside a conductor

Metals conduct because each atom lends a loosely held outer electron that wanders freely. Insulators lack such wanderers, so extra charge placed on them stays stuck where it lands. That single difference explains everything that follows.

At rest, every free charge has stopped moving, which forces the field inside the metal to zero. If a field remained, it would push the free electrons to move, contradicting rest. Excess charge is therefore pushed to the outer surface, and the field just outside stands perpendicular to it.

**Example.** Place a charge at the center of a hollow metal shell. The inner surface gains the opposite charge and the outer surface carries the rest, while the metal itself stays field free. A car body works the same way in a lightning strike, shielding the riders inside.

**Tip.** To locate hidden charge, draw an imaginary surface inside the metal itself. Zero field there means zero enclosed charge, so inner and outer surface charges must balance the interior charge exactly. Let the metal reach rest before applying any of this.

**Recap.** At rest the field inside a conductor is zero, extra charge lives on surfaces, and shells shield interiors.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Applying Gauss's Law to Symmetric Charge Distributions](https://lightmysky.com/learn/science/applying-gausss-law-to-symmetric-charge-distributions-mt_1LZboKPJ4D)

## Opens up

- [Calculating Electric Potential from a Charge Distribution](https://lightmysky.com/learn/science/calculating-electric-potential-from-a-charge-distribution-mt_B4WiVkpH4j)