Physics: Electric Current

Study Notes

Current is a rate quantity, mathematically expressed as a quantity over time.
The symbol I represents current.
The standard metric unit for current is the ampere (A), where 1 ampere = 1 coulomb / 1 second.

The direction of an electric current is conventionally the direction that a positive charge would move.
Electrons are the charge carriers in metal wires, but they move in the opposite direction of the electric field.
The convention of current direction was established by Ben Franklin, who envisioned positive charges as the carriers of charge.

Electric potential is a location-dependent quantity that expresses the amount of potential energy per unit of charge at a specified location.
Electric potential difference is the difference in electric potential between two points.
The standard metric unit for electric potential difference is the volt (V), where 1 volt = 1 joule / 1 coulomb.

Electric potential difference is the energy required to move a charge between two locations.
A battery supplies the energy to do work upon the charge to move it from the negative terminal to the positive terminal.
The movement of charge through an electric circuit is analogous to the movement of water at a water park or the movement of roller coaster cars at an amusement park.

Circuit elements serve as energy-transforming devices.
Examples of energy-transforming devices include light bulbs, motors, and heating elements.
In each device, the electrical potential energy of the charge is transformed into other useful (and non-useful) forms.
The moving charge is doing work upon the circuit element to produce different forms of energy.
The location just prior to entering the circuit element is a high electric potential location, and the location just after leaving the circuit element is a low electric potential location.
The loss in electric potential while passing through a circuit element is often referred to as a voltage drop.

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