Circuit Theory - Chapter 1: Circuit Elements and Signal Waveforms

Flashcards covering introductory concepts of circuit theory, including circuit variables (charge, current, voltage, power), active and passive elements, and basic resistive circuit configurations.

Circuit theory

The fundamental theory upon which all branches of electrical and electronics engineering is built, used to describe analysis techniques for electric circuits.

Electric circuit

A mathematical model that approximates the behavior of an actual electrical system.

Charge ($q$)

An electrical property of the atomic particles of which matter consists, measured in Coulombs ($C$). The charge of 1 electron is $-1.602 \times 10^{-19}$\,$C$ and 1 proton is $1.602 \times 10^{-19}$\,$C$.

Current ($I$)

The rate of charge flow, measured in Ampere ($A$), defined by the mathematical expression $I = \frac{dq}{dt}$. It flows from positive to negative terminals.

Voltage ($V$)

The potential difference between two points, representing the energy ($W$) required to move a unit charge through an element, defined as $V = \frac{dW}{dq}$ and measured in Volts ($V$).

Direct current (DC)

A current or voltage that remains constant with time.

Alternating current (AC)

A current or voltage that varies sinusoidally with time.

Power ($P$)

The rate of doing work or rate of energy transfer, measured in Watt ($W$). It is calculated as $P = \frac{dW}{dt}$ or $P = VI$, where positive power indicates consumption and negative power indicates production.

Active element

A device capable of generating electrical energy, such as ideal current sources and ideal voltage sources.

Ideal current source

A source that supplies a constant current to a circuit regardless of any other conditions present in the circuit.

Ideal voltage source

A circuit element that maintains a prescribed voltage across its terminals regardless of the current flowing through them.

Independent source

An active element providing a specified voltage or current that is completely independent of other circuit elements.

Dependent source

An active element where the source quantity (voltage or current) is controlled by another voltage or current within the circuit.

Passive element

A device that uses or dissipates electric energy, such as resistors, inductors, and capacitors.

Resistor ($R$)

An electrical component that impedes or limits the flow of electrical current in a circuit.

Inductor ($L$)

An electrical component that opposes any change in electrical current.

Capacitor ($C$)

An electrical component that can store electrical charge.

Resistors in series

Circuit elements connected at a single node that carry the same current; the equivalent resistance is the sum of individual resistances: $R_T = \sum_{i=1}^{N} R_i$.

Resistors in parallel

Circuit elements connected at two common nodes that have the same voltage across their terminals; the equivalent resistance is given by $R_T = (\sum_{i=1}^{N} \frac{1}{R_i})^{-1}$.

VCVS

Voltage-controlled voltage source; a type of dependent source.

CCVS

Current-controlled voltage source; a type of dependent source.

VCCS

Voltage-controlled current source; a type of dependent source.

CCCS

Current-controlled current source; a type of dependent source.