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

Basic Concepts of Thermodynamics

Thermodynamics studies the material world by selecting a portion of the universe on which attention is focused, known as a System. The remainder of the universe is considered the environment.

Classification of Thermodynamic Systems

Thermodynamic systems are categorized based on their interaction with the environment:

• Open Systems: These systems can exchange both energy (in the form of work or heat) and matter with their surroundings.
  Example: An open glass of water.
• Closed Systems: These systems can exchange energy with the surroundings but not matter.
  Example: A sealed jar of pickles.
• Isolated Systems: These systems cannot exchange matter or energy with the environment. Consequently, the total amount of energy within

Magnetic Properties

A magnetic field is the region around a magnet where its magnetic action is exerted. Within this region, ferrous materials are attracted to the magnet. Outside this region, no attraction is observed.

The magnetic field is represented by lines of force, conventionally going from the north to the south pole. Like poles repel each other, while opposite poles attract.

Magnetic flux is the number of lines of force passing through a surface within a magnetic field.

Materials that allow magnetic flux to pass through them easily are called permeable. They exhibit low resistance to this flux, a property known as reluctance. When a permeable material is placed in a uniform magnetic field, the lines of force concentrate within it, a phenomenon... Continue reading "Magnetism and Electromagnetism: Properties, Circuits, and Induction" »

Fundamental Concepts of Fields and Work

Force Fields

A force field exists in a space if, by placing a test body within it, this body is subjected to a force.

Types of Fields

• Uniform Field: Force vectors have the same magnitude and direction at all points in space.
• Central Fields: The directions of all force vectors converge on a single point.

Work and Energy Transfer

Work is a mechanism of energy transfer between systems when a force acts.

Conservative Fields

Conservative Fields: Those in which the work done by the field force is independent of the path taken, depending only on the initial and final points.

• The work done by the field force along a closed path is zero.
• In a conservative field, work done against the field force is not lost; it is stored

Introduction to Structures

A structure is a group of elements designed to support various forces. These structures must be rugged, lightweight, and stable. The elements in most structures are bars. The bars support compression efforts when laid flat, supported at its ends. The resistance of the components of a structure depends on the mechanical properties of the materials used and the type of effort that will be subject. The main mechanical properties of materials are: mechanical strength, hardness, elasticity, plasticity, and tenacity. The major forces that can act on a material are: traction, compression, flexure, torsion, and shear. The resilience of the materials to different efforts is called by tests. The tests are standard procedures... Continue reading "Structure: Types, Properties, and Applications" »

The Fundamentals of Motion

Motion is defined as a change in position of a body relative to a reference point. Motion can be determined in two ways:

• By analyzing the trajectory and the relationship between position and time.
• By using the position vector as a function of time.

Concepts for the Study of Kinematics

• Mobile Object: The object in motion.
• Trajectory: The path followed by the mobile object.
• Origin/Reference Point: The point used as a reference to determine the mobile object's position.
• Position: The location of the mobile object relative to the origin.
• Displacement (Δs = s_f - s_i): The change in position of a mobile object between two instants of movement. It is the final position minus the initial position.
• Distance Traveled (e): The total length

Introduction to Optics

Optics is the branch of physics that studies light. Since ancient times, various theories have attempted to explain light and its properties. For example, ancient atomists argued that vision occurs because objects emit images that travel from them to the souls of people, who perceive them through their eyes.

Speed of Light and Refractive Index

The speed of light is finite and varies depending on the medium through which it propagates. The speed of light in a vacuum is represented by the symbol 'c' and has an approximate value of 300,000 km/s. Light reaches its maximum speed in a vacuum; its speed is lower in any other medium.

Fermat's Principle and Rectilinear Propagation

Fermat's principle states that when light travels from... Continue reading "Fundamental Principles of Light: Reflection, Refraction, and Dispersion" »

It's called electrical machine, which is any device capable of generating, processing, or using electricity.
Generators: They are machines capable of generating electrical power from mechanical energy they receive, classified as:
"The current generating dynamo."
"The alternator generates alternating current." Transformers: These are electrical machines that convert electrical current into different features, both voltage and intensity. Motors: These are electrical machines that harness the power they receive and transform it into mechanical energy. Depending on the type of power they receive, we differentiate between DC motors and AC motors. Electric Field: A magnet or electrical current disrupts the spacing around them, giving rise to a... Continue reading "Understanding Electrical Machines: Generators, Motors, and More" »

The Anthropocentric Perspective and the Geocentric Model

Ideas that placed the human species in the center of the universe are known as the anthropocentric perspective. Overcoming this viewpoint has been a slow and costly process, during which scientists have struggled against prejudices, myths, and superstitions.

Ptolemy and the Geocentric System

Ptolemy created a model of the universe with Earth at the center, around which the Moon, Sun, and other stars revolved. Although subsequently proven incorrect, this geocentric model was accepted for centuries. Over time, the practical observation of the sky became more widespread, increasing the number of astronomers and observatories.

Copernicus and the Heliocentric Revolution

The proposed Ptolemaic system... Continue reading "The Shift from Geocentrism to Cosmic Reality" »

Material Properties

Sensory Properties

Sensory properties are those that stimulate our senses, such as color and odor.

Optical Properties

Optical properties describe how a material interacts with light. Materials are classified as:

• Opaque: Do not allow light to pass through.
• Transparent: Allow light to pass through and can be seen through clearly.
• Translucent: Allow light to pass through but cannot be seen through clearly.

Thermal Properties

Thermal properties describe a material's behavior when exposed to heat. They are classified as:

• Conductive: Allow heat energy to pass through (e.g., metal).
• Insulating: Do not allow heat energy to pass through (e.g., glass fiber).

Magnetic Properties

Magnetic properties are determined by a material's behavior in an... Continue reading "Understanding Material Properties and Mechanical Stress Tests" »

Magnetic Fields

A magnetic field is the disturbance produced by a magnet in an area of space. It is manifested by the interactions that occur in that area with other magnets or moving electric currents.

Oersted's Experience and the Lorentz Force

Oersted's experience shows that electric charges at rest do not create magnetic fields, but if they are moving, then they do.

The Lorentz Force: If we introduce a moving charge into a magnetic field, it will experience a force given by the expression...

Similarities and Differences Between Electric and Magnetic Fields: An Analogy

• Both fields are generated by electric charges.
• Electric field strength and magnetic field strength depend inversely on the square of the distance to the point where we make the measurement.