21. electric charge & electric field

Fundamental Forces

The four main forces of nature: gravitational, electromagnetic, strong interaction, and weak interaction.

Gravitational Interaction

The mutual attraction of all objects due to their mass.

Electromagnetic Interaction

Includes electric and magnetic forces.

Strong Interaction

Responsible for holding the nucleus of an atom together.

Weak Interaction

Responsible for radioactivity.

Electric Charge

A property of matter that causes it to experience a force when placed in an electromagnetic field.

Positive Ion

An atom that has lost one or more electrons.

Negative Ion

An atom that has gained one or more electrons.

Ionization

The gain or loss of electrons that creates ions.

Conservation of Charge

The principle stating that the total electric charge in a closed system remains constant.

Quantized Charge

Every observable amount of electric charge is an integer multiple of a basic unit.

Conductors

Materials that allow electric charge to move easily.

Insulators

Materials that do not allow electric charge to move easily.

Coulomb’s Law

States that the electric force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

Point Charge

A charged body that is very small compared to the distance between charges.

Electric Field

A region around a charged particle where a force would be exerted on other charged particles.

Electric Dipole

A pair of equal and opposite charges separated by a distance.

Electric Dipole Moment

The product of the charge and the distance separating the charges.

Torque on Electric Dipole

The force responsible for rotating the dipole in the direction of the electric field.

Potential Energy of Electric Dipole

U = -p • E, where p is the electric dipole moment and E is the electric field.

Superposition of Electric Fields

The principle that the total electric field at a point is the vector sum of the fields produced by individual charges.

Electric Field Line

Imaginary lines showing the direction of the electric field at various points.