Glossary
Capacitor
An electrical component designed to store electric potential energy in an electric field between two conductive plates separated by a dielectric material.
Example:
The flash in a camera uses a capacitor to quickly discharge stored energy, producing a bright burst of light.
Change in electric potential (ΔV)
The difference in electric potential between two points, representing the work done per unit charge to move a charge between those points.
Example:
A 9-volt battery creates a change in electric potential of 9 volts across its terminals, driving current through a connected device.
Charge (q)
A fundamental property of matter that experiences a force when placed in an electromagnetic field; it can be positive or negative.
Example:
An electron carries a fundamental negative charge, which dictates its interaction with electric fields and other charged particles.
Conservation of Electric Energy
The fundamental principle stating that the total electric energy within a closed system remains constant, transforming between different forms but never being created or destroyed.
Example:
In a simple circuit, the chemical energy stored in a battery is converted into electrical potential energy, which then transforms into heat and light in a light bulb, demonstrating the conservation of electric energy.
Coulomb's Law
Describes the electrostatic force between two point charges, stating it is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
Example:
The attractive force holding an electron in orbit around a proton in an atom is precisely described by Coulomb's Law.
Electric Field Strength (E)
A vector quantity representing the force per unit positive charge experienced at a given point in space due to other charges.
Example:
The electric field strength around a charged lightning rod is very high, which helps attract lightning strikes.
Electric Potential (V)
A scalar quantity representing the electric potential energy per unit charge at a specific point in an electric field, independent of the charge placed there.
Example:
A power outlet in your home provides a specific electric potential (voltage) relative to the ground, ready to power appliances.
Electric Potential Energy (U)
The energy a charge possesses due to its position within an electric field, representing the work done to bring that charge from infinity to its current location.
Example:
A charged particle held stationary near another like-charged particle has high electric potential energy due to their mutual repulsion.
Negative work (sign convention)
Occurs when an external force must do work against the electric field to move a charge from a lower electric potential to a higher electric potential, similar to pushing an object uphill.
Example:
To move a positive charge closer to another positive charge, an external force must do negative work against the repulsive electric field.
Positive work (sign convention)
Occurs when the electric field does work on a charge, causing it to move from a higher electric potential to a lower electric potential, similar to an object falling downhill.
Example:
When a positive charge moves from the positive plate to the negative plate of a capacitor, the electric field does positive work on it, increasing its kinetic energy.
Work (W)
A scalar quantity representing the energy transferred when a force acts over a distance, specifically the energy transferred by an electric field on a charge.
Example:
If you push a charged particle against an electric field, the work you do increases its electric potential energy.
Work done by an electric field
The energy transferred when an electric field exerts a force on a charge, causing it to move from one point to another.
Example:
When a positive charge is released in a uniform electric field, the field does work done by an electric field on the charge, accelerating it towards lower potential.
Work-Energy Theorem
States that the net work done on an object equals the change in its kinetic energy, and in the context of electric fields, work done by the field equals the negative change in electric potential energy.
Example:
As a charged particle accelerates through a uniform electric field, the Work-Energy Theorem explains how its initial electric potential energy is converted into kinetic energy.