Title: 12th Grade Electric Charge, Conductors & Insulators
Learning Objectives:
Identify the two types of charges: positive and negative.
Predict charge distributions and the resulting attraction or repulsion in a system of charged insulators and conductors.
Explain how charging by rubbing and charging by induction takes place.
Introduction to Electricity
Explains the fundamental concepts of electricity.
Electrostatics:
Static electricity refers to electricity at rest produced by an imbalance of electrical charges.
The term "electricity" derives from the Greek word "elektron," meaning amber, which can generate static electricity when rubbed with cloth.
Famous Contributors in Electricity:
Benjamin Franklin: Conducted famous experiments with kites in thunderstorms, proving lightning is a form of electricity.
Classified charges as positive or negative.
Famous Contributors in Electricity (cont'd):
Benjamin Franklin: Invented the lightning rod, which helped prevent structural fires by diverting lightning strikes.
Famous Contributors in Electricity (cont'd):
J.J. Thomson: Discovered the electron in 1897 by studying cathode rays (radiation emitted by low-pressure gas under voltage).
Famous Contributors in Electricity (cont'd):
Ernest Rutherford: Discovered protons, which are positively charged particles.
Electric charges are measured in coulombs (C).
Electric Charge and Structure of the Atom:
Atoms consist of three subatomic particles:
Electrons
Protons
Neutrons
Electric Charge:
Electrons carry a negative electric charge; protons carry a positive electric charge.
Interaction of Charges:
Electric charges produce electrical forces.
Unlike charges attract each other.
Interaction of Charges (cont'd):
Like charges repel each other.
Interaction of Charges (cont'd):
Electric forces are reinforced by similar charge behavior—like charges repel.
Charge Separation:
Occurs when an external charged sphere is placed near a neutral sphere, causing a distribution of charges.
Conductors and Insulators - What Are Conductors?
Electrical conductors allow electricity to flow with ease.
Examples: Metals, humans, and earth—explains electric shocks.
Examples of Conductors:
Graphite, human body, and earth.
Common metal conductors:
Copper
Gold
Iron
What Are Insulators?
Insulators hinder free electron flow.
Common examples include:
Plastic
Wood
Glass
Differences Between Conductors and Insulators:
Conductors:
Allow electricity and heat to pass through.
Examples: Silver, aluminum, iron.
Electrons move freely within the material.
Electric field present on the surface.
Insulators:
Do not permit heat or electricity to pass.
Examples: Paper, wood, rubber.
Electrons do not move freely.
No internal electric field.
Methods of Charging - Net Charge:
An object's net charge is the sum of its electrons and protons, categorized as:
Neutral
Negatively charged
Positively charged
Charging by Friction:
Involves electron transfer when two objects are rubbed against each other.
Charging by Conduction:
Also known as charging by contact, it occurs when a charged object touches a conductor.
Charging by Induction:
Charging an uncharged object by bringing it close to a charged object without direct physical contact.
Identify positive and negative charges.
Predict charge distributions and resulting forces in charged systems.
Explain charging methods: rubbing and induction.
Fundamental concepts of electricity.
Static electricity is created by an imbalance of charges, derived from the Greek "elektron" (amber).
Benjamin Franklin: Proved lightning is electricity; classified charges; invented the lightning rod.
J.J. Thomson: Discovered the electron in 1897.
Ernest Rutherford: Discovered protons; measured electric charge in coulombs (C).
Atoms consist of electrons, protons, and neutrons. Electrons carry negative charge, protons carry positive charge.
Unlike charges attract; like charges repel. Electrical forces arise from charge interactions.
Occurs when a charged sphere affects a neutral sphere’s charge distribution.
Conductors: Allow electricity flow (e.g., metals like copper, gold, and iron).
Insulators: Hinder electron flow (e.g., plastic, wood, glass).
Conductors have free-moving electrons; insulators do not.
Net Charge: Sum of electrons and protons classifies objects as neutral, negatively charged, or positively charged.
Charging Methods:
By Friction: Electron transfer by rubbing.
By Conduction: Touching a charged object.
By Induction: Charging without direct contact.