Current Electricity: Potential, Current, and Resistance

Vocabulary practice flashcards covering electric potential, potential difference, electric current, Ohm's law, and resistance from chapter 3: Current Electricity.

Electric Potential

The electric level of charge at a point that determines the direction of the flow of electric charge between two points.

Electric Potential Difference

The amount of work done to carry a unit positive charge from point $A$ to point $B$, defined mathematically as $\text{Potential difference between two points} = \frac{\text{Work}}{\text{Total charge transferred}}$ ($V = \frac{W}{Q}$).

Potential Difference of a Cell

The difference in potential between the positive and negative terminals of a cell, caused by chemical reactions occurring inside the cell, which sets electrons into motion through an external conducting wire.

Volt ($\text{V}$)

The SI unit of potential difference, named in honour of Alessandro Volta, defined as $1\,\text{V} = \frac{1\,\text{J}}{1\,\text{C}}$.

Free Electrons

The outermost electrons of atoms in a metallic conductor that are very weakly bound to the nucleus, can move freely from atom to atom, and act as carriers of negative charge.

Alessandro Volta

The Italian scientist who constructed the first electric cell and in whose honour the unit of potential difference, the volt, was named.

Units for Small Values of Potential Difference

Submultiples of the volt used to measure small potential differences: millivolt ($1\,\text{mV} = 10^{-3}\,\text{V}$) and microvolt ($1\,\mu\text{V} = 10^{-6}\,\text{V}$).

Units for Large Values of Potential Difference

Multiples of the volt used to measure large potential differences: kilovolt ($1\,\text{kV} = 10^3\,\text{V}$) and megavolt ($1\,\text{MV} = 10^6\,\text{V}$).

Motion of Free Electrons in a Conductor

In an unconnected wire, electrons move randomly in all directions. When connected to a cell, an electric force drives the negatively charged electrons from the negative (lower potential) terminal to the positive (higher potential) terminal with a definite non-zero average velocity.

Electric Current ($I$)

The flow of electrons through a conductor, quantitatively defined as the charge ($Q$) passing through the cross-section of a conductor in unit time ($t$), or $I = \frac{Q}{t}$.

Direction of Conventional Electric Current

The direction taken by convention for current flow, going from the positive terminal to the negative terminal of a cell, which is opposite to the direction of the flow of electrons.

Ampere ($\text{A}$)

The SI unit of electric current, named after the French mathematician and scientist Ampere. One ampere is the current flowing when one Coulomb of charge passes through a conductor every second ($1\,\text{A} = \frac{1\,\text{C}}{1\,\text{s}}$).

Charge of an Electron

The fundamental electric charge carried by a single electron, which is equal to $1.6 \times 10^{-19}\,\text{C}$.

Units for Small Values of Current

Submultiples of the ampere used to express small electric currents: milliampere ($1\,\text{mA} = 10^{-3}\,\text{A}$) and microampere ($1\,\mu\text{A} = 10^{-6}\,\text{A}$).

Ohm's Law

A law formulated by George Simon Ohm stating that if the physical state of a conductor remains constant, the current ($I$) flowing through it is directly proportional to the potential difference ($V$) across its ends ($I \propto V$, leading to $V = IR$).

Physical State of a Conductor

The structural and environmental conditions of a conductor in Ohm's law, specifically its length, area of cross-section, temperature, and material composition.

Resistance of a Conductor

The hindrance and opposition to electric current caused by moving electrons colliding with the atoms and ions along their path inside the conductor.

Ohm ($\Omega$)

The SI unit of electrical resistance, named after George Simon Ohm, defined as $1\,\text{Ohm} = \frac{1\,\text{Volt}}{1\,\text{Ampere}}$.

Resistance of One Ohm

The resistance of a conductor when a current of one Ampere ($1\,\text{A}$) flows through it when a potential difference of one Volt ($1\,\text{V}$) is applied between its ends.

Resistivity

The characteristic property of a conductor related to how its resistance ($R$) at a given temperature depends on its length ($L$), area of cross-section ($A$), and material.