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

Material Science Timeline

• 1769: Discovery of the steam engine (Watt)
• 1831: Discovery of the dynamo (Faraday)
• 1913: Popularization of stainless steel
• 1950: Discovery of silicones and first use in aircraft
• 1960: Perfection of silicon crystals (almost perfect purity)
• 1962: Discovery of the nickel and titanium alloy
• 1971: Presentation of soft contact lenses (Bausch & Lomb)
• 1983: First mobile phone
• 1991: First Web page

Second Industrial Revolution Key Points

• New production systems improve accelerated production.
• Amendment to the way we produce at all levels.
• Minimization of production costs.

Plastics: An Overview

Plastics are characterized by their plasticity, a property that allows them to be easily molded into the most convenient shapes. Their history began... Continue reading "Material Science Timeline and Innovations" »

Mechanisms

Mechanisms are devices that transmit motion to perform a job. They are used to transmit motion in two primary ways:

Linear Motion Transmission

1. Fixed Pulleys

   A fixed pulley is a wheel with a grooved edge that rotates around a central axis. A rope or belt passes through the groove. The force applied at one end of the rope equals the resistance at the other (F = R). The advantage of a fixed pulley is the change in the direction of motion.

2. Movable Pulleys

   In a movable pulley, one end of the rope is fixed, and the resistance hangs from the pulley's axle. The force required is half the resistance (F = R/2).

3. Pulley Systems (Hoists)

   A hoist combines fixed and movable pulleys. The force required is calculated as F = R/(2n), where 'n' is the number

Different Properties of Materials

The ability of a resistance material to resist forces without distorting excessively or breaking is a crucial property.

• Toughness

  Toughness is the property that some materials have to withstand forces repeatedly without breaking.

• Resilience

  Resilience is the property of a material to recover its original shape after being deformed by an effort.

• Ductility

  Ductility is the property of certain materials to deform permanently into a thin wire without breaking.

• Malleability

  Malleability is the property of certain materials to deform permanently in the form of a thin sheet without breaking.

• Hardness

  Hardness is the property that indicates the opposition a material offers to being penetrated or scratched.

Different Types of Stresses

• Traction

  Traction

Electrical Protection Devices

Protection devices safeguard electrical installations and connected components from potential overloads. They also protect people from electric shock, preventing current leakage to the ground and the consequent economic damage to the user.

Fuses

A fuse is connected in series with the circuit so that all the current flows through it. It consists of a base with two fixed contacts, a plug-piece cartridge or blade, and fusible material surrounded by a medium that acts as a means of extinction.

• Overload: Occurs when the current value in an electrical installation exceeds the fuse's rating.
• Short circuit: Occurs when a fault in an installation element or an accident causes a sudden surge in current, causing the fuse to blow.

DVD Data Storage

The DVD data zone consists of a highly reflective layer called the land. Projections known as pits rise from this land. These pits represent recorded data. The data track is recorded helically from the inside to the outside of the disc.

Pixelated Images and Freezing

If a DVD player displays pixelated images and freezes with different discs, the first step is to clean the lens.

DVD Photodetector Composition and Function

(Information needed)

DVD Servo Systems

DVD players have five servo systems:

1. Focus Control
2. Track Monitoring
3. Coil Monitoring (Tracking)
4. Sled Servo
5. Disc Speed Control

Symptoms of a Dirty Lens and Cleaning Procedure

A dirty lens can cause various playback issues. Here's how to clean it:

1. Moisten one end of a cotton swab with isopropyl

Cybersecurity Threats: Semantic Attacks and Hoaxes

A semantic attack tricks users into believing they are interacting with a legitimate website, while they are actually interacting with a fake. A hoax is an email containing false information, often inviting the recipient to spread viruses or forward the email to collect email addresses for spam. Hoaxes themselves can be considered a form of semantic attack.

Access Control Measures for Computer Systems

Various access control measures can be implemented on computer systems:

• Human Systems: Security guards.
• Biometrics: Fingerprint, voice, and iris recognition.
• Electronics: Security cameras, sensors, and electronic locks.
• Logic: Magnetic cards and passwords.

Understanding Interrupt Requests (IRQ)

An Interrupt

Simple Machines

Simple machines are basic devices formed by a single element. Their primary function is to multiply human force. Ancient philosophers identified five key simple machines: the lever, the wheel and axle, the inclined plane, the screw, and the wedge.

Types of Machines

• Drive Machines: These machines focus solely on producing motion.
• Operational Machines: These machines perform specific tasks, such as a vacuum cleaner.

Elements of a Machine

• Mechanisms: Moving parts that transmit motion to other machine components.
• Structure: Supports the mechanisms.
• Engine/Motor: Generates motion or force.

Force

Force is anything that can change the motion of a body or cause deformation. It is measured in Newtons (N). Approximately 0.1 N is the force exerted... Continue reading "Simple Machines and Mechanisms" »

Why Must an Ohmmeter be Calibrated When Changing Ranges?

What is Calibration?

An ohmmeter must be calibrated each time you change the measuring range to verify the proper operation of the instrument. When calibration is not performed, the needle may deflect incorrectly on the ohmmeter scale. Calibration involves measuring a known resistance standard and comparing it with the ohmmeter reading. This should be done at several points on the instrument's scale and for various scales.

Connecting an Ammeter to Measure Current Through a Resistor

Series vs. Parallel Connection

In which of the two forms mentioned would you connect an ammeter to measure the intensity of current flowing through resistor R? Justify your answer.

The correct way to connect an ammeter... Continue reading "Ohmmeter Calibration and Circuit Analysis Techniques" »

When you need to make a motion transmission, you usually work directly with axes: We support a fixed, usually cylindrical axis, which serves as another element, such as a wheel or a pulley, to turn around. Tree: It's a bar, usually cylindrical, that transmits circular motion. Coupling: The element that allows joining two trees or two axes. Wheel Bearings: These are two completely smooth rim wheels that are in direct contact with one another for moving forward. Gearboxes: We have a minimum of two formed mechanisms, sprockets, constructed in such a way that matches the outgoing motion and transmits circular motion and power. Types of Gears: Cylindrical straight, helical, and bevel. A series of small items would not be possible without the proper... Continue reading "Understanding Motion Transmission Mechanisms in Machinery" »

Palmer Micrometer: Precision Measurement

A Palmer micrometer is a direct-reading measuring instrument. It provides the length value directly, enabling measurements with a precision of 0.01 mm and, in some models, 0.001 mm.

Micrometer Parts

• Body
• Tube
• Rotating drum
• Friction screw
• Circular graduation
• Linear graduation
• Brake
• Mobile probe
• Fixed and insulating probe handles

Micrometer Management

A micrometer can be used to measure parts on marble, on machines, or as support for serial investigations. The measurement procedure is as follows:

1. Open the tool to a range slightly greater than the dimension to be measured.
2. Position the piece between the probes.
3. Gently rotate the drum until the probes support against the piece. This should be done by acting through the