Glossary
Conservation of Energy
The principle of conservation of energy states that the total energy of an isolated system remains constant, meaning energy can transform between kinetic, potential, and other forms but is neither created nor destroyed.
Example:
As an electron accelerates from rest through an electric potential difference, its initial electric potential energy is converted into kinetic energy, demonstrating the conservation of energy.
Coulomb's Constant
Coulomb's constant (k) is a proportionality constant used in Coulomb's Law and formulas for electric potential and potential energy, relating electric force to charge and distance.
Example:
When calculating the force between two point charges, Coulomb's constant ensures the units and magnitude are correct, typically having a value of approximately .
Electric Field Lines
Electric field lines are visual representations used to depict the direction and strength of an electric field, originating from positive charges and terminating on negative charges.
Example:
Near a positive point charge, electric field lines radiate outwards, showing the direction a positive test charge would accelerate.
Electric Potential (Voltage)
Electric potential, or voltage, is the electric potential energy per unit charge at a specific point in an electric field, representing the 'push' available to move a charge.
Example:
A 9-volt battery provides an electric potential difference of 9 Joules per Coulomb, capable of driving current through a circuit.
Electric Potential Energy ($U_e$)
Electric potential energy is the energy a charge possesses due to its position within an electric field or relative to other charges.
Example:
Two like charges pushed close together have high electric potential energy because work was done against their repulsive electric force to bring them near.
Equipotential Lines
Equipotential lines are lines or surfaces in an electric field where the electric potential is constant, meaning no work is done by the electric field when a charge moves along them.
Example:
Around a positive point charge, equipotential lines are concentric circles, indicating that all points on a given circle have the same electric potential.
Equipotential Surfaces
Equipotential surfaces are three-dimensional surfaces in an electric field where every point on the surface has the same electric potential.
Example:
For a charged sphere, the equipotential surfaces are concentric spherical shells surrounding the charge, perpendicular to the radial electric field lines.
Volt (V)
The Volt is the SI unit for electric potential and electric potential difference, defined as one Joule of energy per Coulomb of charge (J/C).
Example:
A standard wall outlet in the US provides an electric potential difference of 120 Volts, indicating the energy available per unit charge.
Work Done by Electric Forces
Work done by electric forces refers to the energy transferred when a charge moves within an electric field, often resulting in a change in the charge's electric potential energy.
Example:
When a positive charge is released in a uniform electric field, the electric field does positive work done by electric forces on the charge, causing it to accelerate and its potential energy to decrease.