Technology and Engineering Lecture: Electronics, Processing, Materials, and Design

Vocabulary review flashcards covering electrical circuits, plastic forming and classification, metal oxidisation protection, food preservation techniques, and technological design methodology.

Dry Cell

A direct current ($\text{DC}$) input source operating at $1.5\,\text{V}$, featuring a zinc anode, a copper cathode, and a liquid electrolyte that conducts electricity.

Photovoltaic Cell

A silicon-based direct current ($\text{DC}$) power source that releases electrons when exposed to sunlight.

AC Generator

An electrical power source where motor coils produce a magnetic field, resulting in alternating current that flows in both directions.

Diode

A semiconductor circuit component that allows current flow in only one direction, marked with a silver band on its cathode side.

LED (Light Emitting Diode)

A light-emitting semiconductor component whose longer terminal lead indicates the positive ($$+$) connection.

Transistor

A three-terminal electronic component composed of a base, emitter, and collector that serves to amplify electrical current.

Resistor

A passive electrical component that restricts or limits the flow of current in a circuit.

Capacitor

An electrical component (polarized or non-polarized) that stores electrical charge and provides a "time delay" in circuits.

LDR (Light Dependant Resistor)

An input sensor whose electrical resistance ($\Omega$) is determined by the intensity of incident light.

Thermistor

A temperature-sensitive sensor categorized with PTC or NTC coefficients where temperature controls resistance.

Ohm's Law

The fundamental circuit relationship stating that voltage and resistance are directly proportional, whereas current and resistance are inversely proportional ($V = I \times R$).

Resistor 4-Band Colour Code

A colour-coding method where bands 1 and 2 give base numerical digits, band 3 provides the decimal multiplier, and band 4 indicates tolerance (e.g., gold represents $\pm 5\%$).

Engineering Notation Prefixes

Standard power-of-ten multipliers used in engineering: $10^3$ represents kilo ($\text{k}$), $10^6$ represents mega ($\text{M}$), and $10^9$ represents giga ($\text{G}$).

Thermoplastics

A class of plastics that can be repeatedly softened and reshaped (re-used) upon the application of heat.

Thermosetting Plastics

A category of plastics that undergo a permanent chemical change upon setting and cannot be remelted or reshaped with heat.

Extrusion (Plastics)

A plastics manufacturing process that produces continuous plastic strands, predominantly utilized for making piping.

Injection Moulding

A shaping process where plastic pellets are placed in a hopper, melted, and injected into a mould cavity.

Press Moulding

A manufacturing method where plastic material is positioned between two mold halves and pressed together.

Vacuum Forming

A thermoforming method in which a thin, heated sheet of plastic is drawn over a mold using suction.

PET (Plastic Type 1)

Polyethylene terephthalate; a durable and waterproof plastic used in items such as baby bottles and beverage containers.

Hot-Dip Galvanizing

A metal coating method that immerses metals in molten zinc, producing a white powder residue that provides an extra barrier against oxidisation ("rust").

Electroplating

A process of coating a cathode object by passing electricity through a solution containing an anode metal (such as copper, gold, or silver), forming a layer that thickens over time.

Staple Food

The primary food source consumed by the largest portion of a population, such as maize or mealie meal.

Pickling

A food preservation technique utilizing vinegar inside sealed glass containers (e.g., pickles, achar) to inhibit bacterial growth through high acidity.

Canning

A food preservation method utilizing sucrose (sugar solution) or brine (salt solution) to inhibit bacteria by creating adverse osmotic conditions.

Blast Freezing

A preservation method involving extreme cold applied very rapidly, halting bacterial growth completely compared to ordinary deep freeze storage.

Smoking (Food)

A method of preserving meat and fish (e.g., smoked ham) where antibacterial chemical compounds present in fire smoke destroy bacteria.

Grain Processing Sequence

The step-by-step agricultural process of handling cereal grains: Harvest $\rightarrow$ Thresh $\rightarrow$ Winnow $\rightarrow$ Dry $\rightarrow$ Store.

IDMEC

An acronym representing the stages of the technological design and problem-solving process: Investigate, Design, Make, Evaluate, and Communicate.