Physics Flashcards: Current, Kirchoff's First Law, and Drift Velocity

A set of vocabulary flashcards covering basic current concepts, Kirchoff's first law, electron number density, mean drift velocity, potential difference, and electromotive force.

Current

The rate of flow of charge.

Ammeter

A device used to measure electric current.

Coulomb

The unit of electric charge.

Electron Charge

The negative charge carried by an electron, equal to $1.6 \times 10^{-19}\,C$.

Current Equation ($I$)

The rate of flow of charge given by $I = \frac{\Delta Q}{\Delta t}$, where $I$ is current in amperes ($A$), $\Delta Q$ is change in charge in coulombs ($C$), and $\Delta t$ is change in time in seconds ($s$).

Cation

A positively charged ion.

Anion

A negatively charged ion.

Kirchoff's First Law

At any point in a circuit, the sum of the currents into that point is equal to the sum of the currents out of that point.

Current in a Series Circuit

A circuit condition where the current stays the same at all points.

Current in a Parallel Circuit

A circuit condition where the current is shared across branches.

Number Density ($n$)

The number of free electrons per cubic meter ($m^{-3}$) of material.

Insulator Number Density

A very low number density of free electrons, around $10^9\,\text{electrons}\,m^{-3}$, as seen in materials like plastic.

Semiconductor Number Density

A moderate number density of free electrons, around $10^{17}\,\text{electrons}\,m^{-3}$, as seen in materials like silicon and germanium.

Conductor Number Density

A high number density of free electrons, around $10^{28}\,\text{electrons}\,m^{-3}$, as seen in materials like gold and copper.

Mean Drift Velocity Equation

The equation $I = A n e v$, relating current ($I$), cross-sectional area ($A$), electron number density ($n$), electron charge ($e = 1.6 \times 10^{-19}\,C$), and mean drift velocity ($v$).

Potential Difference (P.D.)

The energy transferred by each coulomb of charge by components, represented by symbol $V$ and calculated using $V = \frac{W}{Q}$.

Electromotive Force (E.M.F.)

The energy transferred to each coulomb by energy sources (such as a cell or generator), represented by symbol $E$ and calculated using $E = \frac{W}{Q}$.