Basic Electronic Parameters and Components

Voltage: The difference in charge between two points, measured in Volts.
Current: The flow of electrons through a conductor or semiconductor, measured in Amperes (Amps). Some materials conduct better than others (conductors, semiconductors, insulators.) Current flows from positive to negative.
Power: Determines the work a circuit can do, measured in Watts (Watts = Volts × Amps).
Ground: The minimum voltage reference level. True ground is connected to the earth, but circuits might be battery-powered resulting in a floating ground.

Resistance

Resistors: Measured in Ohms, placed between conductors and insulators to control current and voltage drops in a circuit.
Resistance Control: Limit current flow to prevent damage to components like the LED (light emitting diode). Resistors dissipate energy as heat; the greater the current, the hotter the resistor.
Resistor Tolerance: Resistors aren't always precise, so tolerances (e.g., ±10%) are given to indicate a range of possible values.
Resistor Color Code: A system of colored bands on resistors that represent their values and tolerance.
Potentiometers: Variable resistors that change resistance by rotating a knob. Linear or logarithmic types are used, affecting how resistance changes with rotation.

Circuit Components

Circuits: Closed loops of current flow, with the sum of current entering a junction equal to the sum of current exiting; breaks in a circuit create an open circuit; circuits with low resistance create a short circuit.
Switches: Mechanical devices that interrupt the current flow, described by the number of poles and the number of throws.
Voltage Divider: In a series circuit with two resistors, the sum of the voltage drop across each equals the total voltage drop. The voltage between two resistors can be calculated using the voltage divider formula.
Alternating Current (AC): Voltage that periodically reverses direction, sinusoidally, whereas Direct Current (DC) voltage is unidirectional. The root mean square (RMS) voltage value is 1/√2 of the peak voltage.
Inductors: Used as AC filters and in electromagnets. The strength of their magnetic field is affected by factors such as the number of turns in the coil, coil size, spacing, and core material.
Transformers: Devices that change the voltage of AC signals. The ratio of turns between the primary and secondary coils determines whether the voltage is stepped up or stepped down. The power (V*I) remains the same in both coils.
Relays: Switches activated by electromagnets; these can carry AC or DC current. They're slow, noisy, and generate voltage spikes when the magnetic field collapses. Resistive loads turn current into heat.
Capacitors: Components that store electrical charge. They are typically composed of two separated metal plates with a non-conducting material (dielectric) between them. Increasing the plate size, or adding a dielectric increase capacitance.
Capacitor Types: Electrolytic and non-electrolytic types with different dielectrics and usage. Electrolytic capacitors are polarized, requiring correct orientation and with a greater capacitance.
Electrolytic vs. Non-Electrolytic capacitors: Electrolytic are capable of storing more charge but have a polarity, are slower to leak, whereas non-electrolytic, lacking polarity, store less charge.
RC Time: The time it takes a capacitor to charge or discharge is controlled by a resistor and is proportional to RC.
Semiconductors: Materials with electrical conductivity between conductors and insulators. They are the most important invention of the 20th century. Free electrons from the donor atoms in a semiconductor create 'holes' or positively charged spaces also capable of carrying a current.
Diodes: One-way electrical valves. They conduct electricity in one direction and block it when current is reversed. They can be used as rectifiers to convert AC to DC.
Transistors: Three-terminal devices that control current flow. They are either Bipolar Junction transistors, or Field-Effect transistors. Switching or amplifying, they form the core of many modern electronics devices
LEDs (Light Emitting Diodes): Light-emitting diodes; they produce light at the junction of the semiconductor when electrons combine with holes. The color depends on the impurity in the material.
The Transistor: Modern electronics use transistors for switching (on/off) currents and amplification (increasing currents)
Comparators: Compare signals, sending a high or low output depending on whether the input signal is greater or less than a reference
Digital vs Analog representation: Analog representation of data is continuous and digital signals represent data in binary numbers (0s/1s), via pulses.