AP Physics 2: Foundations of Electrostatics

Electric Charge

A fundamental property of matter, exists in two types: positive and negative.

Two Types of Charge

Positive (+) and negative (-) charges associated with protons and electrons respectively.

Quantization of Charge

The concept that electric charge comes in discrete packets, specifically integer multiples of the elementary charge.

Elementary Charge (e)

The smallest unit of electric charge, approximately equal to 1.60 x 10^-19 Coulombs.

Coulomb (C)

The SI unit of electric charge, representing a large quantity of charge.

Law of Conservation of Charge

States that the net electric charge of an isolated system remains constant over time.

Conductors

Materials in which electrons can move freely, allowing for the conduction of electric charge.

Insulators

Materials where electrons are tightly bound to atoms, preventing movement of charge.

Charging by Friction

A method of charging objects by rubbing two insulators together, leading to electron transfer.

Charging by Conduction

A method where a charged object directly touches a neutral object, allowing charge transfer.

Charging by Induction

Charging a conductor without contact by polarizing it and providing a grounding path for charge movement.

Coulomb's Law

Describes the electric force between two point charges as proportional to the product of their charges and inversely proportional to the square of the distance between them.

Coulomb's Constant (k)

The proportionality constant in Coulomb's Law, approximately equal to 8.99 x 10^9 N·m²/C².

Electric Force (F_E)

The force exerted between two charged objects, measured in Newtons (N).

Superposition Principle

The principle that the net force on a charge is the vector sum of the forces from all other charges.

Repulsive Force

The force that pushes two like charges apart from each other.

Attractive Force

The force that pulls two opposite charges toward each other.

Mass of Electron (m_e)

Approximately 9.11 x 10^-31 kg, the mass of an electron.

Mass of Proton (m_p)

Approximately 1.67 x 10^-27 kg, the mass of a proton.

Electric Field

A field around charged objects that exerts force on other charges placed within the field.

Vector Nature of Force

Electric forces have both magnitude and direction, which must be considered when calculating net forces.

Comparison of Electric and Gravitational Force

Electric forces can be both attractive and repulsive, while gravitational forces are always attractive.

Charge Interaction Rule

Like charges repel each other, while opposite charges attract each other.

Equilibrium Condition of Conductors

In electrostatic equilibrium, excess charge resides on the surface and the electric field inside is zero.

Friction (Triboelectric Effect) Example

Using a balloon and hair to transfer electrons and create a charge.

Unit Conversion in Physics

The necessity to convert units, particularly in charge and distance, before applying formulas for electric forces.