Glossary
Amperes (A)
The SI unit for electric current, defined as one Coulomb of charge passing per second (C/s).
Example:
A standard household outlet can deliver up to 15 Amperes (A) of current.
Conventional Current
The defined direction of current as the direction positive charges would move, from higher to lower potential.
Example:
Even though electrons flow towards the positive terminal, we say Conventional Current flows from the positive terminal of a battery.
Current (I)
A quantitative measure of the amount of charge (Q) passing through a cross-sectional area of a wire per unit time (t).
Example:
A car battery might supply a Current (I) of 5 Amperes to start the engine.
Drift velocity
The average velocity attained by charged particles, such as electrons, in a material due to an electric field.
Example:
The Drift velocity of electrons in a typical household wire is surprisingly slow, often less than a millimeter per second, despite the current moving at nearly the speed of light.
Electric current
The flow of electric charge, typically through a wire or other conductive material.
Example:
When you turn on a light switch, electric current flows through the wires to power the bulb.
Electric potential difference (voltage or emf, ε)
The driving force that pushes electric charges through a circuit, analogous to pressure in a fluid system.
Example:
A 9-volt battery provides an electric potential difference that makes charges move through a small circuit.
Electron Flow
The actual movement of electrons (negative charge carriers) in a circuit, which is in the opposite direction of conventional current.
Example:
In a copper wire, the Electron Flow is from the negative terminal of the battery towards the positive terminal.
No Net Current
A state where there is no overall directional movement of charge carriers, even though individual charges may still be moving randomly.
Example:
Inside an uncharged metal, electrons are moving randomly, but there is No Net Current because their movements cancel out.