Direct Current Circuits Practice Flashcards

30 vocabulary flashcards covering basic principles of direct current circuits including symbols, current flow, potential difference, resistance, and resistivity.

Electric Current

The flow of charged carriers, such as free electrons in a metal or ions in a solution or plasma.

Coulomb ($C$)

The unit of charge, equivalent to the charge that passes through a given section of a conductor when a steady current of $1\,\text{ampere}$ flows for $1\,\text{second}$ ($As$).

Elementary Charge ($e$)

The smallest value of charge, equivalent to $1.602 \times 10^{-19}\,C$; both electrons and protons carry this magnitude of charge.

Conventional Current

Current that is set to flow from the positive terminal of a battery to the negative terminal, in the direction of positive charge flow.

Charge Carrier Density ($n$)

Defined as the amount of charge carriers per unit volume ($n = N/V$), measured in $m^{-3}$.

Average Drift Speed ($v_d$)

The identical average speed at which all charge carriers move through a conductor, related to current by $I = nAqv_d$.

Potential Difference ($V$)

A measure of the electrical energy transferred per unit charge ($V = W / Q$) between two points in a circuit; also known as voltage drop.

Volt ($V$)

The unit of potential difference, equivalent to one joule per coulomb ($J/C$).

Electrical Resistance ($R$)

The ratio of the potential difference ($V$) across a component to the current ($I$) flowing through it ($R = V/I$).

Ohm's Law

States that the current through a metallic conductor is directly proportional to the potential difference across it, provided temperature and other physical conditions remain constant.

Ohmic Conductor

A material, such as a metallic conductor at constant temperature, that obeys Ohm's Law.

I–V Characteristic

A graph showing the variation of current with potential difference used to investigate the relationship between electricity and components.

Filament Lamp

A non-Ohmic conductor whose resistance increases with current because of the increasing temperature of its tungsten filament.

Semiconductor Diode

A non-Ohmic component that conducts current when forward biased but has near-infinite resistance when reverse biased.

Barrier Voltage ($V_d$)

The specific voltage at which a diode's resistance starts to drop; for silicon, it is between $0.6\,V$ and $0.7\,V$.

Thermistor

A 'thermal resistor' made from a semiconductor or metal oxide where charge carrier density and resistance are sensitive to temperature changes.

Positive Temperature Coefficient (PTC) Thermistor

A type of thermistor whose resistance increases as the temperature increases.

Negative Temperature Coefficient (NTC) Thermistor

A type of thermistor whose resistance decreases as the temperature increases.

Light-Dependent Resistor (LDR)

A component where the electrical resistance decreases as light intensity increases.

Resistivity ($\rho$)

An intrinsic property of a material that determines resistance, defined by the expression $R = \frac{\rho L}{A}$.

Ohm metre ($\Omega\,m$)

The standard unit used for resistivity ($\rho$).

Electrical Power ($P$)

The rate at which resistance converts electrical energy into other forms of energy such as heat or mechanical energy.

Watt ($W$)

The unit of electrical power, which can be expressed through the relationships $P = VI$, $P = I^2R$, and $P = \frac{V^2}{R}$.

Free Electrons

The specific charge carriers responsible for conducting electricity in a metal.

Ions

The charge carriers that facilitate electric current in a solution or in a plasma.

Junction of Conductors

Commonly known as a node, it is a point in a circuit symbol where multiple conductors meet.

Fixed Resistor

A component that obeys Ohm's Law at constant temperature, resulting in a constant ratio of $V$ to $I$.

Lattice Vibrations

The vibrations of atoms within a metal; their amplitude increases at higher temperatures, causing more collisions and higher resistance.

Avogadro constant ($N_A$)

A constant representing the number of particles in a mole, given as $6.02 \times 10^{23}$, used to calculate total charge from the number of protons or electrons.

Quantization of Charge

The principle that the charge on any charge carrier is a multiple of the elementary charge ($e$).