Notes, summaries, assignments, exams, and problems for Technology

Resistors

Resistors slow down and restrict the flow of current. Resistance is measured in Ohms (Ω).

Types of Resistors

There are two main types: fixed and variable.

Variable Resistors

• Potentiometer / Rheostat: A type of resistor whose value can be modified by a movable piece. These can be used as volume controls on audio equipment or light dimmers.
• Thermistors: These are resistors that depend on temperature. There are two types:
  • NTC (Negative Temperature Coefficient): As temperature increases, resistance decreases.
  • PTC (Positive Temperature Coefficient): As temperature increases, resistance increases.
  • Used as temperature detectors in thermostats.
• LDR (Light Dependent Resistor): The resistance varies according to the amount of light the resistor receives.

Understanding Computer Networks

A computer network is a set of computers connected to each other, enabling them to share resources and exchange information. They can share printers, files, folders, and Internet connections.

Ethernet Classification

The two common types of Ethernet networks are 100Base-T and 1000Base-T.

The number indicates the transmission speed in Megabits per second: 100Mbps and 1000Mbps, respectively.

The letter 'T' indicates the type of cable used to transmit data. The cable consists of twisted pairs of copper wire with RJ45 connectors at each end. These cables are used to connect the network.

Types of Cables

• Twisted Pair UTP: 8 copper wires twisted together in 4 pairs with an RJ45 connector at the end.
• STP: A safer cable for transmitting

Wood

Pith: the middle part of the trunk

Heartwood: hardest and darkest, best part for woodwork

Sapwood: recent growth used for more artistic woodwork

Bark: exterior layer, protects the plant from outside attacks

Cambium: thin transparent layer of live cells

Hardwood

Beech: used in furniture and floors because it bends and is easily shaped

Oak: used in parquet floors, boats, etc.

Mahogany: used in joinery, musical instruments, etc.

Softwood

Pine: used in electrical posts, boats, etc.

Silver fir: used in building, carpentry, etc.

White poplar: used in frames, paper, etc.

Engineered Wood

Plywood: formed by gluing together thin sheets with synthetic resins

Chipboard: made with wood shavings and chips which are glued together

Fibreboard: fibers come from grinding

Carpentry

Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM)

Scanning Tunneling Microscopy (STM)

Scanning Tunneling Microscopy (STM) is an instrument used for imaging surfaces at the atomic level, revealing the topography of conductive specimens. It measures tunneling current and can be used in air, water, and various gas environments, at temperatures ranging from near zero Kelvin to a few hundred degrees Celsius. STM operates in two modes: constant interaction mode and constant height mode.

Advantages of STM

• High resolution, not limited by diffraction
• Small sample size
• Can modify samples to create small structures
• Does not require a partial vacuum

Disadvantages of STM

• Difficult to determine detailed shapes
• Slow scanning speed
• Small image sizes
• Not

A file is a set of ordered documents that are related by some circumstance or event. It is essential for a company to have a file, that is to sort and classify documentation in a particular way.

Why Document Management is Important

• It allows to keep, store, and safeguard information
• Information can be easily and quickly found
• To comply with the law
• It can help in the decision-making process

Types of Files

1. Active: Documents that are currently being used and queried
2. Semi-active: Documents no longer effective but kept for legal reasons
3. Inactive: Documents not valid but with a historical or documentary value

File Systems

The file system is the criterion used for ordering information.

• Alphabetical: Information classified in the order of the alphabet. The ordering

What is Gas Used for in a Residential Building?

Gas provides the energy needed for a comfortable home, powering systems like:

• Heating systems
• Water heating systems
• Kitchen stoves

Gas Supply Methods and Types

How is Gas Supplied?

Gas can be supplied through:

• Pipelines: Natural gas is transported via an underground network.
• Cylinders: Butane and propane are commonly transported in cylinders.

Which Gases are Used?

Common residential gases include:

• Natural gas (pipelines)
• Butane (cylinders)
• Propane (cylinders and pipes)

Gas System Components

General Valve

The general valve controls the entire gas supply to the building.

Main Gas Supply Unit

The main gas supply unit, typically located in the street, connects the main gas line to the individual property line. It's... Continue reading "Residential Gas Systems: A Comprehensive Guide" »

Seed Drill - Jethro Tull

He perfected a horse-drawn seed drill in 1700 that economically sowed the seeds in neat rows (1714). He later developed a horse-drawn hoe.

Four Crop Rotation - Lord Townshend

Flying Shuttle - John Kay

The flying shuttle was one of the key developments in the industrialization of weaving during the early Industrial Revolution. It allowed a single weaver to weave much wider fabrics, and it could be mechanized, allowing for automatic machine looms.

Spinning Jenny - James Hargreaves

The spinning jenny is a multi-spindle spinning frame and was one of the key developments in the industrialization of weaving during the early Industrial Revolution. It was invented in 1764 by James Hargreaves in Stanhill, Oswaldtwistle, Lancashire,... Continue reading "Key Inventions of the Industrial Revolution" »

Unit 3: Network Computing and Protocols

Firewall: A software program that helps screen out hackers, viruses, and worms that try to reach your computer over the internet.

ADSL: A device used to connect a computer or router to a telephone line which provides the DSL service to connect to the internet broadband communications technology.

Router: This is a hardware device that routes data from a local area network (LAN) connection.

How Does Network Computing Work?

• IP Address: A numerical label assigned to each device.
• HTML: The language for creating web pages.
• URL Address: The protocol used for referencing online addresses.

Communication Protocols

• TCP: The suite of communications protocols used to connect hosts on the internet.
• FTP: An open protocol standard

Essential Electronic Components

Relays

Relays are components used to control a high voltage current by means of a small current applied to a coil. When an electric current passes through the coil, it acts like an electromagnet and attracts a movable piece of metal that closes two contacts. If an electric current doesn't flow through the coil, the central contact stays joined to the contact on the left.

Capacitors

These are components that can store electric charge. They are made of two conductive plates separated by a non-conductive material called a dielectric. There are two kinds of capacitors: electrolytic and non-electrolytic capacitors. Electrolytic capacitors have terminals of different lengths, while non-electrolytic capacitors have terminals... Continue reading "Essential Electronic Components: Relays, Capacitors, and More" »