Topic 1: DC Electric Circuits - Fundamentals

These vocabulary flashcards cover the fundamental definitions, elements, units, and laws of DC electric circuits based on the provided lecture materials.

Electric circuit

A set of devices and objects forming a path for electric current, where electromagnetic processes are described using electromotive force, current, and voltage.

Electric conduction current

The directed movement of free electric charge carriers $q$ in matter or vacuum, characterized by i = rac{dq}{dt} and measured in Amperes ($A$).

Electric transfer current

Electric current carried by the transport of electric charges by physical bodies.

Electric displacement current

The sum of displacement current in vacuum and polarization current of a dielectric, equal to the time derivative of the electric displacement flux $D_S$.

Total electric current

A scalar value equal to the sum of conduction current, transfer current, and displacement current through a specific surface.

Direct current (DC)

The constant and unidirectional movement of charged particles where I = rac{q}{t}, and $q$ is the total charge in Coulombs ($C$) over time $t$ ($s$).

Electron charge value

The smallest negative charge possessed by an electron, equal to $-1.602 \times 10^{-19}\,C$; therefore, $1\,C = 6.24 \times 10^{18}$ electrons.

Electric potential ($\phi_a$)

The work required to move a unit charge ($1\,C$) from a given point $a$ to infinity; measured in Volts ($V$).

Electric voltage ($U$)

The work spent on transferring a unit charge ($1\,C$) from point $a$ to point $b$, calculated as $U = \phi_a - \phi_b$.

Electromotive force (EMF)

A scalar quantity characterizing the ability of a non-electrical or induced field to cause electric current, equal to work $W$ in Joules divided by charge $q$ ($E = \frac{W}{q}$).

Circuit diagram (Schema)

A graphical representation of an electric circuit containing conventional symbols for elements and showing their connections.

Equivalent circuit (Substitution scheme)

A mathematical model of an electric circuit containing ideal passive (resistive, inductive, capacitive) and active elements.

Resistor

A passive element intended for using its electrical resistance $R$ ($Ohm$); its component equation is $U_R = R \times I_R$.

Electrical conductivity ($G$)

The inverse of resistance ($G = \frac{1}{R}$), measured in Siemens ($S$).

Inductor (Inductive coil)

A passive element intended for using its self-inductance $L$ or its magnetic field; stores energy as $W_L = \frac{L \times i_L^2}{2}$.

Inductance unit (Henry)

A unit equal to $\frac{V \cdot s}{A} = Ohm \cdot s = H\,(\text{Henry})$.

Capacitor

A passive element intended for using its electrical capacitance $C$ ($F$), storing energy in an electric field as $W_C = \frac{C \times u_C^2}{2}$.

Branch (Ветвь)

A section of an electric circuit along which a single electric current flows.

Node (Узел)

A junction point in an electrical circuit where at least three branches are connected.

Loop (Контур)

A sequence of circuit branches forming a closed path.

Independent Voltage Source (IVS)

An electrical energy source characterized by EMF $E$ and internal resistance $R_{BT}$, defined by the external characteristic $U = E - R_{BT} \times I$.

Independent Current Source (ICS)

An electrical energy source characterized by current $J$ and internal conductivity $G_{BT}$, defined by $I = J - G_{BT} \times U$.

Ideal Voltage Source

A source where $R_{BT} = 0$ and the voltage $U = E$ is constant regardless of the current.

Ideal Current Source

A source with infinite internal resistance ($R_{BT} = \infty$) where the current $I = J$ is independent of the load resistance.

Kirchhoff's First Law (KCL)

States that the algebraic sum of currents at a node is zero: $\sum I_k = 0$.

Kirchhoff's Second Law (KVL)

States that the algebraic sum of EMFs in a loop equals the algebraic sum of voltage drops: $\sum E_k = \sum U_k$.

Source Transformation (CS to VS)

A method to replace a current source ($J, G_{BT}$) with a voltage source ($E, R_{BT}$) using formulas $R_{BT} = \frac{1}{G_{BT}}$ and $E = R_{BT} \times J$.

Number of independent loops ($k_H$)

Calculated based on the number of branches $B$ and nodes $U$ as $k_H = B - (U - 1)$.