Insulators and Conductors

Jul 15, 2024

Insulators and Conductors

Overview

  • Materials Classification: Simplified into insulators and conductors.
    • Caveat: There are also semi-conductors, super conductors, and other electrical materials.

Atomic Structure

  • Both insulators and conductors: Composed of atoms with positively charged nuclei and negatively charged electrons.
  • In both: Positively charged nuclei cannot move freely in solids.
  • Electrons: The key difference between insulators and conductors.
    • Conductors: Electrons move freely.
    • Insulators: Electrons do not move freely.

Behavior under Electric Field

  • Conductors: Need an external force (like a battery) to move electrons.
    • Electrons migrate freely in response to electric fields.
  • Insulators: Electrons are stuck despite external electric fields.
    • Atoms can polarize; nuclei and electrons can shift slightly, creating interactions without electron flow.

Adding Extra Charge

  • Insulators:
    • Charges are stuck; can distribute or localize them.
  • Conductors:
    • Extra charges move to the surface, spreading out to minimize repulsion.
    • Net charges reside on the outer edge.

Examples of Materials

  • Insulators: Glass, wood, plastics.
  • Conductors: Metals (e.g., gold, copper, silver).

Interaction Examples

  • Charging by Contact: Touching charged conductor to another conductor spreads the charge.
  • Charging by Induction: Bringing a charged object near a conductor induces redistribution of charges without direct contact.
    • Grounding: Conducting path allows electrons to move to/from a large reservoir (ground).

Practical Demonstration

  • Induced Charge on a Can: Proximity causes redistribution of charges, such as moving an uncharged soda can.
  • Balloon Example: Rubbing a balloon transfers electrons, making it negatively charged, and it sticks to surfaces by polarizing the atoms in the wall/ceiling.