Glossary
Charge
A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field.
Example:
An electron carries a fundamental unit of negative charge, while a proton carries a positive charge of the same magnitude.
Conductors
Materials that allow electric charge carriers (typically electrons) to move freely through them.
Example:
Copper wires are excellent conductors because their electrons are loosely bound and can easily flow, enabling electricity to pass through.
Coulomb's Law
A fundamental law describing the electrostatic force between two point charges, stating it is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.
Example:
Coulomb's Law is used to calculate the attractive force between a proton and an electron in a hydrogen atom.
Coulomb's constant (k)
A proportionality constant in Coulomb's Law, representing the strength of the electrostatic interaction in a vacuum.
Example:
The value of Coulomb's constant (k) is approximately , which is crucial for calculating electric forces.
Coulombs (C)
The SI unit of electric charge, representing the amount of charge transferred by a constant current of one ampere in one second.
Example:
A lightning bolt can transfer several coulombs (C) of charge from the clouds to the ground in a fraction of a second.
Electric Polarization Model
A model that describes how electrons within a material rearrange themselves when an external electric field is applied, leading to a separation of positive and negative charges.
Example:
The Electric Polarization Model helps explain why an uncharged insulator can still be attracted to a charged object.
Electrically neutral
A state where an object or system contains an equal amount of positive and negative charges, resulting in no net electric charge.
Example:
Most macroscopic objects, like a table or a book, are electrically neutral because they have an equal number of protons and electrons.
Electrostatic force
The attractive or repulsive force between two charged objects at rest, as described by Coulomb's Law.
Example:
When you rub a balloon on your hair, the electrostatic force causes your hair to stand on end as it's attracted to the balloon.
Elementary charge (e)
The smallest unit of electric charge observed in nature, equal to the magnitude of charge on a single electron or proton.
Example:
The charge on a single electron is exactly one negative elementary charge (e).
Gravitational forces
The attractive force between any two objects with mass, as described by Newton's Law of Universal Gravitation.
Example:
The Earth's gravitational forces keep the Moon in orbit around it.
Insulators
Materials that restrict the movement of electric charge carriers, preventing the free flow of electricity.
Example:
Rubber gloves act as insulators, protecting electricians from electric shock by preventing current from flowing through their bodies.
Like charges
Charges that have the same sign (both positive or both negative).
Example:
Two positively charged balloons will repel each other because they are like charges.
Opposite charges
Charges that have different signs (one positive and one negative).
Example:
A positively charged glass rod will attract a negatively charged silk cloth because they are opposite charges.
Permittivity in Matter
A measure of how easily a material can be polarized by an electric field, differing from the permittivity of free space due to the material's composition.
Example:
The permittivity in matter for water is much higher than for air, which affects how electric fields behave in aqueous solutions.
Permittivity of free space (ε₀)
A fundamental physical constant representing the ability of a vacuum to permit electric field lines, appearing in equations related to electric fields and forces.
Example:
The speed of light in a vacuum is related to both the permittivity of free space (ε₀) and the permeability of free space.
Point charges
Idealized charged objects whose size is negligible compared to the distances between them, simplifying calculations of electrostatic interactions.
Example:
When calculating the force between two charged spheres far apart, we can often treat them as point charges located at their centers.
Scalar
A physical quantity that has magnitude but no direction.
Example:
Temperature is a scalar quantity, as it only describes how hot or cold something is, not a direction.