Magnetic Fields and Electronics Fundamentals

Comprehensive vocabulary flashcards covering magnetism, electromagnetism, semiconductors, circuit laws, and timing components based on lecture notes.

Magnetic Field

A region where magnetic forces can act, represented by the symbol $B$ and measured in the unit tesla ($T$).

Right-Hand Rule (Straight Wire)

A method to determine the direction of the magnetic field around a wire: point the thumb in the direction of the current ($I$) and the fingers curl in the direction of the field ($B$).

Magnetic Field Strength (Straight Wire)

The formula used to calculate the field strength at a distance $r$ from a long wire: $B = \frac{\mu_0 I}{2\pi r}$.

Permeability of Free Space ($\mu_0$)

A constant used in magnetic calculations, equal to $4\pi \times 10^{-7}\,T\,m/A$.

Solenoid

A cylinder-shaped coil of wire that creates a strong and uniform magnetic field inside when carrying current, described by $B = \mu_0 n I$, where $n = \frac{N}{L}$.

Right-Hand Rule (Solenoid)

A rule where fingers curl in the direction of current loops and the thumb points toward the solenoid's north pole.

Transformer

A device consisting of a primary and secondary coil on an iron core that uses a changing magnetic field to transfer electrical energy and change voltage levels.

Faraday’s Law

The principle stating that an induced voltage is created by a changing magnetic flux: $V = -N \frac{d\Phi}{dt}$.

Magnetic Flux ($\Phi$)

A measure of the magnetic field passing through a specific area, roughly defined as $\Phi = BA$.

Ideal Transformer Voltage Equation

The relationship between primary and secondary coils: $\frac{V_s}{V_p} = \frac{N_s}{N_p}$.

Ideal Transformer Power Balancing

The principle that power is conserved in an ideal transformer ($P_p = P_s$), resulting in $V_p I_p = V_s I_s$.

Magnetic Force on a Wire

The force experienced by a current-carrying wire in an external magnetic field: $F = BIL\sin(\theta)$, which is strongest at $\theta = 90^\circ$.

Commutator

A split metal ring in a DC motor that reverses current direction every half-turn to maintain constant torque in one rotational direction.

Relay

An electrically controlled switch that uses a solenoid to move a metal armature, allowing a small control current to manage a larger load circuit.

Speaker

A device that converts electrical signals into sound by using the magnetic force $F = BIL$ to vibrate a cone back and forth.

Microphone

A device that converts sound waves into electrical signals by using sound vibrations to move a coil through a magnetic field, inducing a voltage ($V$).

AC Voltage Sine Wave

The mathematical model for alternating current voltage: $V(t) = V_{\max}\sin(2\pi f t + \phi)$, where $f$ is frequency and $\phi$ is phase shift.

RMS Voltage ($V_{rms}$)

The effective voltage of an AC signal, calculated as $V_{rms} = \frac{V_{\max}}{\sqrt{2}}$; for example, $120\,V_{rms}$ has a peak of approximately $170\,V$.

Diode

A semiconductor device with an anode and cathode that acts as a one-way valve, allowing current only when forward-biased (anode at higher voltage).

Depletion Region

The barrier at a PN junction where charges combine; it shrinks during forward bias to allow flow and expands during reverse bias to block it.

Diode Equation

The mathematical model of diode current: $I = I_s(e^{\frac{V_d}{n V_t}} - 1)$, representing an exponential current-voltage relationship.

Rectifier

A circuit, such as a bridge rectifier using four diodes, that converts alternating current (AC) into pulsating direct current (DC).

Ripple Voltage ($V_{ripple}$)

The residual variation in DC output after rectification and smoothing, estimated for full-wave rectifiers as $V_{ripple} \approx \frac{I}{f C}$.

Bipolar Junction Transistor (BJT)

A current-controlled device with three terminals (Collector, Base, Emitter) where a small base current ($I_b$) controls a larger collector current ($I_c$).

Transistor Regions of Operation

The three states of a BJT: Cutoff (OFF), Active (linear amplification where $I_c = \beta I_b$), and Saturation (fully ON acting as a closed switch).

LED (Light-Emitting Diode)

A diode that releases energy as photons (light) when forward-biased, typically requiring a current-limiting resistor calculated by $R = \frac{V_{supply} - V_{LED}}{I}$.

Inductor ($L$)

A coil of wire that stores energy in a magnetic field and resists changes in current flow, with a unit of henries ($H$).

Inductor Voltage Equation

The formula for induced voltage across an inductor due to changing current: $V = L\frac{dI}{dt}$.

Inductive Energy

The energy stored in the magnetic field of an inductor: $E = \frac{1}{2} L I^2$.

RL Time Constant ($\tau$)

The value defining how fast current changes in an inductor-resistor circuit: $\tau = \frac{L}{R}$.

Inductive Reactance ($X_L$)

The opposition an inductor offers to alternating current: $X_L = 2\pi f L$.

555 Timer Pin 2 (Trigger)

The pin that starts timing and sets the output high when the voltage falls below $1/3\,V_{CC}$.

555 Timer Pin 6 (Threshold)

The pin that ends timing and sets the output low when the voltage rises above $2/3\,V_{CC}$.

Monostable Mode (555)

A 'one-shot' circuit configuration where a trigger pulse generates a single output pulse of width $t \approx 1.1 R C$.

Astable Mode (555)

An oscillator configuration with no stable state, creating a continuous square wave with frequency $f \approx \frac{1.44}{(R_A + 2R_B)C}$.

Ohm's Law

The fundamental circuit relationship defined as $V = I \times R$, used to calculate voltage, current, or resistance.

Kirchhoff’s Current Law (KCL)

The principle that the total current entering a junction must exactly equal the total current exiting that junction.

Kirchhoff’s Voltage Law (KVL)

The principle that the sum of all voltage drops in any closed loop must equal zero, meaning provided energy equals consumed energy.