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

Common Electrical Risks

The most likely risks in electrical installations are electrical discharges caused by direct or indirect contact. These discharges can cause severe consequences such as muscle contractions, respiratory failure, and burns.

Risks can also be caused by a malfunction of protection systems or a failure of the grounding system.

Types of Electrical Contact Hazards

Direct Contact Risks

Direct contact occurs when a person touches the active parts of an electrical installation, i.e., a live conductor. A poor connection can lead to direct contact due to damaged or fallen insulation.

Indirect Contact Risks

According to the REBT (Low Voltage Electrotechnical Regulations), indirect contact occurs when conductive parts, normally not live,... Continue reading "Electrical Safety: Preventing Common Hazards" »

Understanding Electric Current and Circuits

Electric current is the passage of electrical charge through a conductor. This occurs when there is an imbalance of charge between two points of the conductor.

An electric circuit is a set of elements connected together through which electric current flows. For current to flow, the circuit must be closed.

Components of an Electric Circuit

• Generator: Builds and maintains the voltage needed to produce the current.
• Conductors: Pathways through which the electric current flows, usually made of copper or aluminum.
• Receivers: Elements that transform electrical energy into other forms of energy.
• Switching and Control Elements: Direct the flow of electrical current.
• Protection Elements: Protect individuals and the

Electric Motors: Construction and Operation

Current Motors: Establishment and Operation

Constitution

The constitution of these motors is determined by the need to establish a magnetic field and to have a series of coils traversed by electric current, and located within the field. They consist of two main elements: the stator and the rotor.

• The stator is the fixed part of the motor, responsible for establishing the magnetic field. It has a number of coils, called spools, placed around the poles of an electromagnet. These poles are attached to the housing.
• The rotor is the moving part of the motor. It consists of another set of coils, called induced coils, which are wound on the slots of an iron core that is called induced. The ends of the coils are

Texts and Communicative Purpose

Texts can be classified according to three criteria: diction, message content, or communicative purpose. An expository text, for example, can encompass humanities and journalism simultaneously.

Classifying Texts by Purpose

• Informative: Transmit events, general information, data, or knowledge.
• Prescriptive: Direct, order, advise, instruct, or prescribe.
• Persuasive: Convincing, persuading, i.e., modifying receiver behavior.
• Rhetorical: Have an aesthetic purpose, capturing the receptor's attention through beauty, etc.

Language Features and Text Codes

To achieve the communicative purpose, messages included in the text must adapt to their communicative intent.

Text Types by Language Function

Texts, depending on the predominant... Continue reading "Text Classification: Purpose, Language, and Codes" »

Mesh Law

The principle of conservation of energy is applied to circuits through the Mesh Law. Connect a series circuit of three resistors and check that the sum of voltages (measured in each) coincides with the voltage at the terminals from the source. The algebraic sum of all potential differences over a closed path (mesh) in the circuit is zero. That is, Σ ΔV = 0 for a closed course. This theorem is simply a particular way of stating the Principle of Conservation of Energy in electrical circuits, which can be explained from the potential difference defined in terms of work and energy.

Node Law

The principle of conservation of electric charge is expressed through the Node Law. A node is a point where the circuit is divided into branches, but... Continue reading "Circuit Analysis: Mesh, Node Laws, and Passive Elements" »

Text Properties: Appropriateness and Consistency

Appropriateness in Text

Appropriateness refers to the property of a text that meets social, personal, linguistic, and situational norms. A text is considered appropriate when it:

• Fits the intended theme.
• Adapts to the person issuing it or the person receiving it.
• Is suitable for the situation or place in which it is presented.
• Effectively achieves its intended aim.
• Adjusts the tone or level of formality to the situation.
• Respects the social rules of a group.
• Adapts to the level of language used in the communication.
• Follows the rules of courtesy.

Consistency in Text

Consistency is the property of a text that gives it unity and meaning, allowing for proper interpretation. A text is considered consistent if:... Continue reading "Text Properties: Appropriateness and Consistency in Communication" »

Kinds of Signs

Signs can be classified in several ways:

By Channel

• Acoustic: Perceived through hearing (e.g., spoken words, music).
• Tactile: Perceived through touch (e.g., Braille, a handshake).
• Visual: Perceived through sight (e.g., written text, traffic lights).
• Olfactory: Perceived through smell (e.g., perfume, smoke).
• Gustatory: Perceived through taste (e.g., the flavor of food).

By Relation with the Referent

• Evidence (Index): Has a physical relationship with the referent (e.g., smoke indicating fire).
• Icons: Bear some resemblance to the reality they represent (e.g., a photograph, a drawing).
• Symbols: Bear no inherent relation to their referent; the connection is conventional (e.g., the word "dog", a national flag).

The Linguistic Sign

• Signifier: The

Electronic Components

• Fixed Resistors:
  • Limit the amount of current flowing through a circuit.
  • Protect certain components.
• Potentiometer: Provides variable resistance. They regulate the amount of current that passes through the circuit.
• Variable Resistance with Temperature:
  • NTC (Negative Temperature Coefficient): If the temperature increases, the resistance decreases.
  • PTC (Positive Temperature Coefficient): If the temperature increases, the resistance increases.
• Variable Resistance with Light (LDR):
  • Decreases its resistance value when the amount of light it receives increases.
  • If the resistance decreases, the current intensity increases.
• Capacitor: Stores electrical charge for later use.
  • Its capacity is the ratio of electric charge stored to the voltage

Mass Media

Mass media refers to channels used to transmit messages to large populations, such as newspapers, radio, and cinema. Our society relies heavily on their constant presence.

Characteristics of Mass Media

• Complex technology requiring specialized professionals.
• Collective receivership (messages reach multiple people simultaneously).
• Primarily unidirectional communication (limited feedback from receivers).

Mass media are powerful instruments of social influence, serving three main purposes: informing, shaping public opinion, and entertaining.

Verbal and Nonverbal Codes

Each medium employs unique communicative codes. For example, the press utilizes images, headlines, and text layout, while television incorporates sets, gestures, and music.

Television

Television... Continue reading "Mass Media and Dialects of Castilian" »

Rigid Couplings

Rigid couplings are those which have a rigid connection between the two axes. Generally, they are built with two plates that are joined together by means of screws. They do not allow any relative movement between the two elements joined.

Torque Limiters

Torque limiters are rigid, maintaining the transmission of the effort while not exceeding a certain value. The most basic are constructed by a cross pin which is sheared when the torque limit is exceeded. They are simple and economical but have the disadvantage of being removed each time they are sheared. They are used as security features.

Elastic Couplings

Elastic couplings are those that allow some relative movement between the two axes united. Therefore, they have some elastic... Continue reading "Mechanical Couplings and Clutches: Types and Applications" »