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

Basic Electrical Concepts

Voltage (Tension)

Voltage (also known as Tension or electromotive force) is the energy with which a generator is able to push electrons through a circuit.

Electric Current (Intensity)

Electric Current (or Intensity) is the number of electrical charges flowing through a circuit per unit time. It is measured in amperes (A).

Resistance

Resistance is the opposition a material offers to the flow of electric current. Materials with high resistance make it difficult for electricity to pass through. Resistance is measured in ohms (Ω).

Electric Power

Electric Power indicates the rate at which a device performs its function. The power consumed by a receiver is directly related to the voltage and current that feed the circuit. Power... Continue reading "Fundamentals of Electricity and Circuit Principles" »

Questions and Answers About Materials

1. What Kinds of Natural Fiber Fabrics Are There?

• a) Plant and animal fibers, including those of seaweeds.
• b) Plant and animal fibers.
• c) Plant, animal, and mineral fibers.
• d) Animal and seaweed fibers.

2. What Fibers Are Manufactured Without the Use of Any Natural Product?

• a) All use natural products.
• b) Synthetic.
• c) Artificial.
• d) Both b and c.

3. What Characteristic Should a Fabric Have If It Will Be in Contact With Skin for Many Hours?

• a) Tensile strength.
• b) Hygroscopy.
• c) Resistance to chemicals.
• d) Soft to the touch.

4. The Origin of Plastic Can Be:

• a) Natural and artificial.
• b) Natural, artificial, and synthetic.
• c) Elementary, artificial, and natural.
• d) Natural and recycled.

5. The Degree of Polymerization Is:

• a)

Obtention of Metals

Metals are extracted from ore found in mines. This process involves several stages to obtain pure aluminum. The enrichment of the mineral prepares the mined product for subsequent actions. The main processes of enrichment include:

• Crushing: Mechanically reducing the size of the rocks.
• Concentration: Separating the ore from waste material using physical means.
• Reduction: Extracting the maximum amount of the desired chemical element.
• Refinement: Achieving maximum purity.

Aluminum

Aluminum is the most abundant element in the Earth's crust, making up about 7%. Although abundant, it is difficult to obtain. It is produced through electrolysis in a cryolite bath, which is relatively inexpensive. The process has two main phases: obtaining... Continue reading "Aluminum Production and Material Properties" »

Understanding Cryptography: Key Concepts

Confidentiality: Prevents the disclosure of information.

Authentication: The act of establishing or confirming that something or someone is authentic.

Integrity: Prevents the modification or destruction of unauthorized information. Passive threat.

Symmetric vs. Asymmetric Keys

Symmetric Key: In symmetric key systems, the same key is used to encrypt and decrypt.

Asymmetric Key: In asymmetric key systems, encryption uses one key, and decryption uses a complementary key.

Cryptography Explained

Cryptography is the art of writing messages with a secret key or in an enigmatic way. It's a branch of mathematics, informatics, and telematics that uses mathematical methods and techniques to encrypt messages or files through... Continue reading "Understanding Cryptography: Confidentiality, Integrity, and Authentication" »

Chains

Drawbacks of Chains

A drawback of chains is the production of vibrations during operation.

Chain Rollers

Chains consist of inner and outer plates. Pins connect these plates. The outer plates are thicker than the inner plates, with larger holes. Rollers rotate freely on the pins, minimizing friction between the chain and the sprockets.

Chain Cassettes

Cassettes are similar to rollers but without the rolling action. They are more economical and suitable for short chains with light loads.

Chain Blocks

Block chains are designed for heavy loads. They consist of outer plates, pins, and solid blocks between consecutive links.

Chain Links

Links are angled plates that serve as both outer and inner plates. The advantage is the adjustability of chain length... Continue reading "Chains and Belts: Power Transmission Explained" »

Car Clutch Systems

Mission

The clutch's primary function is to progressively transfer engine power, enabling smooth vehicle movement without stalling.

Main Function

A clutch operates by pressing a disc between two flat plates. This pressure causes the disc to rotate, transmitting the engine's rotational force (torque) to the gearbox.

Clutch Disc

The clutch disc transmits motion from the flywheel to the gearbox shaft. It must possess two key qualities:

1. Progressive Engagement (Clutching): The disc should smoothly engage, allowing gradual power transfer.
2. Secure Grip (Locked): Once engaged, the disc must firmly grip to transmit torque effectively.

Dual-Mass Flywheel

A dual-mass flywheel (DMF) consists of primary and secondary masses connected by a damping... Continue reading "Understanding Car Clutch Systems: Types, Functions, and Components" »

Material Hardness: Resistance to Deformation

Hardness is the resistance a material offers to being penetrated or scratched by another material. This property is primarily due to the cohesive forces between the atoms of the material. Hardness is compared and measured using various types of tests.

Generally, the more penetration achieved by applying the same force, the softer the material being studied will be.

Brinell Hardness Test

The Brinell hardness test uses a hard spherical indentor, typically made of tungsten carbide, which is situated above the sample material to be tested. A specific load is applied to the sphere for a defined period. After removing the load and the indentor, the diameter of the indentation left on the specimen is measured... Continue reading "Understanding Material Properties: Hardness, Toughness, Fatigue, Thermal" »

Building Material Characteristics

Flooring Materials

Ceramic Flooring

• Formed by mixing water and clay, then molded and baked.
• A glazed layer of silica and aluminum is applied to the smooth surface, providing enamel-forming qualities such as resistance and impermeability, meeting standards like GCN 1400.

Terrazzo

• Consists of white cement mixed with chunks of marble and granite, compacted and vibrated before curing.
• Pros: Economical, durable, brilliant color after grinding/polishing.
• Cons: Can be slippery, requires more labor.

Hydraulic Tiles

• Consist of two layers: the lower layer is a lean mixture of sand and cement, while the upper layer contains marble sand or silica and Portland cement.

Types of Flooring

• Terrazzo tiles
• Porcelain tiles
• Ceramic tiles
• Extruded

Mechanical Fasteners and Machine Elements

Riveted Joints

Riveting is a method for joining flat pieces of thin material without welding. A rivet, which has a pre-formed head on one end, is inserted into pre-drilled holes in the pieces to be joined. The other end of the rivet is then deformed (e.g., by hammering or pressing) to create a second head, securely fastening the components.

Common applications include:

• Lap Joints: Where two pieces overlap.
• Butt Joints: Where pieces are in the same plane and joined by a single cover plate (riveted).
• Double Cover Plate Butt Joints: Using two cover plates, one on each side, riveted to the main pieces.

Cotter Pins

Cotter pins are steel components designed to be inserted into specific notches, recesses, or holes... Continue reading "Essential Machine Elements: Fasteners, Springs, Bearings, and Lubricants" »