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.