Electrical and Electronic Systems Practice Flashcards

Comprehensive vocabulary flashcards covering introductory electrical engineering concepts, circuit analysis (DC and AC), passive components (resistors, capacitors, inductors), energy distribution, and semiconductor devices (diodes, op-amps, and transistors) based on Braden Phillips and Wen Soong's lecture series.

Charge ($q$)

A quantity of electrical energy measured in coulombs ($C$). The basic charged particles are electrons with a charge of $-1.60 \times 10^{-19}\,C$ and protons with a charge of $1.60 \times 10^{-19}\,C$.

Current ($i$)

The flow of charge measured in amperes ($A$) or coulombs per second, defined as $i = \frac{dq(t)}{dt}$. Reference direction is indicated by an arrow on circuit diagrams.

Voltage ($v$)

The potential difference or electrical potential between two points measured in volts ($V$), equivalent to $J \cdot C^{-1}$. It is the energy required to move $1\,C$ of charge between two points.

Ground

The reference point in an electrical circuit, taken to have a potential of $0\,V$. A circuit with no connection to ground is described as floating.

Passive Reference Configuration

A convention for element labeling where the reference direction for current $i$ points from the positive sign of voltage $v$ through the element to the negative sign. In this state, power is calculated as $p = v \times i$.

Kirchhoff’s Current Law (KCL)

The principle stating that because charge does not accumulate at a node, the sum of currents entering any node is zero.

Kirchhoff’s Voltage Law (KVL)

The principle stating that the sum of potential differences (voltages) around any closed loop in a circuit is zero.

Ohm’s Law

The relationship governing an ideal resistor stating that voltage is proportional to current: $v = \pm i \times R$, where $R$ is resistance measured in ohms ($\Omega$).

Conductance ($G$)

The reciprocal of resistance ($G = \frac{1}{R}$), measured in siemens ($S$). The formula for Ohm's law using conductance is $i = G \times v$.

Ideal Independent Voltage Source

An electrical element that produces a specified voltage across its terminals regardless of the current passing through it.

Ideal Independent Current Source

An electrical element that produces a specified current regardless of the voltage across its terminals.

Resistors in Series

A configuration where two or more resistors share the same current and can be combined into a single equivalent resistance calculated as $R_{eq} = R_1 + R_2 + \dots + R_n$.

Resistors in Parallel

A configuration where two or more resistors share the same voltage and can be combined into a single equivalent resistance calculated as $R_{eq} = \frac{1}{R_1^{-1} + R_2^{-1} + \dots + R_n^{-1}}$.

Battery Storage Capacity

The amount of stored charge in a battery measured in ampere-hours ($A \cdot h$). $1\,A \cdot h$ is equivalent to $3600\,C$.

Internal Resistance ($R_s$)

A model element used to represent the drop in a battery's terminal voltage ($V_t$) as the current drawn from it increases.

Efficiency ($\eta$)

The ratio of output power to input power ($\eta = \frac{P_{out}}{P_{in}}$), usually expressed as a percentage. In linear systems, it can be expressed as $\eta = \frac{R_l}{R_s + R_l}$.

Maximum Power Transfer

A condition where the power delivered to a load is maximized by matching the load resistance to the source resistance ($R_l = R_s$). Efficiency at this point is $50\%$.

Capacitance ($C$)

The property of a device to store charge and energy in an electric field, measured in farads ($F$). The governing equation is $q = C \cdot v$ or $i = C \frac{dv}{dt}$.

DC Steady State

A condition where voltages and currents are no longer changing with time ($\frac{dv}{dt} = 0$ and $\frac{di}{dt} = 0$), causing capacitors to act as open circuits and inductors to act as short circuits.

Inductance ($L$)

The property of a device to store energy in a magnetic field, measured in henries ($H$). The governing equation is $v(t) = L \frac{di(t)}{dt}$.

Period ($T$)

The time taken for a sinusoidal function to repeat itself, related to angular frequency as $T = \frac{2\pi}{\omega}$ and measured in seconds ($s$).

Frequency ($f$)

The number of cycles per second, measured in hertz ($Hz$), where $f = \frac{1}{T} = \frac{\omega}{2\pi}$.

Root-Mean-Square (RMS)

A value for AC quantities that produces the same average power as an equivalent DC quantity. For sinusoidal signals, $V_{rms} = \frac{V}{\sqrt{2}}$.

Impedance ($Z$)

A complex number measured in ohms ($\Omega$) representing the relationship between voltage and current phasors ($V = I \cdot Z$). It consists of resistance ($R = \Re(Z)$) and reactance ($X = \Im(Z)$).

Phasor

A way to represent a steady state sinusoidal function $A \cos(\omega t + \phi)$ using a complex number $A \angle \phi$.

Transformer

An AC device made of two coils wound around an iron core used to step voltage up or down based on the turns ratio $N_1 : N_2$, defined by $\frac{V_2}{V_1} = \frac{N_2}{N_1}$.

Synchronous Speed ($n_s$)

The speed of the rotating magnetic field in an AC machine, calculated for a machine with $N$ pole pairs as $n_s = \frac{60f}{N}\,rpm$.

Induction Motor

The most common type of AC motor where the rotor spins at a speed less than the synchronous speed, relying on relative motion with the stator field to induce current.

Complex Power ($S$)

The product of voltage and current phasors ($S = \frac{1}{2}VI^* = P + jQ$), where $Real\,Power\,P$ is in watts ($W$) and $Reactive\,Power\,Q$ is in volt-ampere reactive ($VAR$).

Power Factor

The cosine of the power angle ($\cos(\theta)$). It indicates the relationship between real power and apparent power.

Back EMF ($E$)

The voltage induced in a DC machine as conductors move through the stator's magnetic field, defined by $E = k \cdot \omega$.

Stall Torque ($\tau_{stall}$)

The torque produced by a DC machine when its rotational speed is zero, occurring when the back EMF ($E$) is zero.

Diode

A two-terminal semiconductor device that allows current flow in one direction (forward biased) and blocks it in the other (reverse biased). The forward voltage drop is typically $\approx 0.7\,V$.

Zener Diode

A special silicon diode designed to conduct in the reverse breakdown region at a specific Zener voltage ($V_Z$) without damage.

Operational Amplifier (Op-amp)

An integrated circuit differential voltage amplifier characterized by very high gain ($A$), high input resistance ($R_{in}$), and low output resistance ($R_{out}$).

Summing-Point Constraint

A rule for analyzing ideal op-amps with negative feedback which assumes the voltages at the inverting and non-inverting inputs are equal and that no current flows into the inputs.

Integrator

An op-amp circuit configuration where the output voltage is the integral of the input voltage, resulting in $v_{out}(t) = -\frac{1}{RC} \int v_{in}(t)\,dt$.

MOSFET

A Metal-Oxide-Silicon Field Effect Transistor; a three-terminal voltage-controlled device where the gate-source voltage ($v_{GS}$) determines the current between the drain and source.

Bipolar Junction Transistor (BJT)

A three-terminal current-controlled device (base, collector, emitter) where a small base current ($i_B$) controls a much larger collector current ($i_C = \beta i_B$).

Pulse-Width Modulation (PWM)

A technique for creating a variable effective DC voltage by rapidly switching a high DC voltage on and off, used to control the speed of DC motors.

H-bridge

A circuit using four transistors as switches to control the speed and direction of rotation for a DC motor by reversing the polarity of the applied voltage.