Topic: Electric charges, the physics behind static electricity.
Competencies: Understanding of static electricity and electrostatics.
Static Electricity
Occurs when an object has a net positive or negative electric charge.
Electrostatics: Interaction between electric charges at rest.
Atomic Structure
Atom Components:
Neutrons: Neutral charge, found in the nucleus, mass = 1.65 x 10^-27 kg.
Protons: Positive charge, found in the nucleus, charge = 1.6 x 10^-19 C, mass = 1.73 x 10^-27 kg.
Electrons: Negative charge, found in the valence shell, charge = -1.6 x 10^-19 C, mass = 9.11 x 10^-31 kg.
Free Electrons & Ionization
Free Electrons: Found in the outermost shell, easily transferred by forces like friction or heat.
Ionization:
Positive Ion: Atom loses electrons.
Negative Ion: Atom gains electrons.
Types of Electric Charges
Discovered by Benjamin Franklin: Positive (protons) and negative (electrons) charges.
Law of Electrostatic Force
Principle:
Like charges repel each other.
Opposite charges attract each other.
Law of Conservation of Charges
Electrons are never created or destroyed, only transferred between materials.
Methods of Charging
Charging by Friction: Transfer of electrons between objects in contact.
Charging by Contact: Distribution of electrons to achieve charge balance.
Polarization: Separation of charges within an object.
Charging by Induction: No direct contact, involves moving charges within an object.
Grounding
Method to safely transfer excess electrons to the earth, a neutral entity.
Electrical Forces
Coulomb's Law:
Describes the magnitude of the electric force between two point charges.
Formula: F = k (q1 * q2) / r^2
Coulomb's Constant (k): 8.988 x 10^9 N m^2/C^2, or approximately 9 x 10^9 N m^2/C^2.*
Summary
Atoms: Composed of neutrons, protons, and electrons.
Charges: Electrons are negatively charged, protons positively charged, with equal magnitude of 1.6 x 10^-19 C.
Charging Methods: Friction, induction, polarization, and contact.
Conservation of Charges: Electrons can be transferred, not created/destroyed.
Coulomb's Law: Force between interacting charges.
Conclusion
Quote from Nikola Tesla: "The day when we shall know exactly what electricity is will chronicle an event probably greater more important than any other recorded in the history of human race."