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

Current Density

The electric current density is a vector quantity representing power per unit area. It relates to current as:

• I is the electric current in amperes (A).
• j is the current density in amperes per square meter (Am^-2).
• S is the area in square meters (m²).

Isolated Point Charges

Current density relates to charge carriers (electrons, holes, ions) by:

Where:

• n_i is the concentration of carrier i.
• q_i is the electric charge of carrier i.
• v_i is the average velocity of carrier i in the volume.

Electromotive Force (EMF)

Electromotive force maintains a potential difference in an open circuit or produces current in a closed circuit. It's a generator characteristic, explained by an electric field Ξ, where defines the EMF.

EMF is the work done to move a... Continue reading "Understanding Current Density and Electromotive Force" »

Introduction to Transformer No-Load Testing

The no-load test of a transformer is performed by feeding one of its windings with rated voltage and frequency, while the other winding is open-circuited. This test provides the value of iron losses and the no-load current (I₀), allowing for the display of its waveform and observation of its characteristic bell shape.

Test Objectives and Fundamentals

Understanding Iron Losses

The power absorbed by a transformer operating under no-load (or vacuum) conditions primarily represents the iron losses, as copper losses are practically negligible due to the small no-load current. Iron losses in a transformer are composed of two main components:

• P0: Power absorbed under no-load conditions (total iron losses)
• PFe:

Key Concepts of Heat and Temperature

1. What is the relationship between heat and kinetic energy?

   The relationship is directly proportional. Heat is a measure of the total kinetic energy of the individual particles in a substance. The higher the kinetic energy of the particles, the hotter an object feels.

2. How is temperature defined?

   Temperature is a measure that indicates how hot or cold an object is. It represents the average kinetic energy of the particles within that object.

3. Is heat the same as energy in transit?

   Yes, heat is a form of energy in transit. It is the energy that is transferred from one object to another due to a temperature difference between them.

4. When does thermal contact occur?

   Thermal contact occurs when heat can be transferred between

Uniform Rectilinear Motion

Newton's Corpuscular Theory of Light

This theory, proposed by Isaac Newton (1642-1726), posits that light consists of tiny particles of matter, called corpuscles, emitted at high speed from luminous bodies in a straight line. The direction of propagation of these particles is known as a ray of light. Key principles of Newton's theory include:

• Rectilinear Propagation: Light travels in a straight line because the corpuscles move at high speed.
• Reflection: It is known that light reflects when hitting a mirror. Newton explained this phenomenon by stating that light particles are perfectly elastic, and therefore, reflection adheres to the laws of elastic collision.
• Refraction: The change in light speed and propagation direction when passing through

Understanding Wave Motion

Wave motion is a form of energy transmission that is not accompanied by the transport of matter. It is the propagation of a vibration, i.e., the propagation of movement around the equilibrium position of a body.

A wave is the position taken at each instant by the disturbance that has occurred.

Types of Waves

• Mechanical waves originate when a disturbance occurs in an elastic medium, which would not exist without the spread.
• Electromagnetic waves, although they may be transmitted through certain media, do not necessarily need an elastic medium and can propagate in a vacuum.

Wave Characteristics

• In longitudinal waves, the vibrations of particles around their equilibrium point occur in the same direction in which the wave propagates.

Motion and Kinematics

Reference Systems and Motion

A reference system is a point from which the movement of a body is observed. The temporal reference system indicates the starting time for studying a movement, represented by the letter T, with the SI unit of seconds (s). A body's movement involves changes in its position over time relative to a spatial and temporal reference system. Kinematics is the branch of physics that studies motion.

Position and Trajectory

Position indicates a body's location with respect to a reference system at a given time. The trajectory is the set of points through which a body moves concerning a reference system. Trajectories can be classified as:

• Rectilinear motion: The trajectory is a straight line.
• Curvilinear motion:

Physics Problems: Work, Energy, and Forces

This document presents a series of physics problems focusing on concepts of work, energy, and forces, followed by their detailed solutions. These exercises are designed to reinforce understanding of fundamental mechanics principles.

Problem Statements

• Problem 1: Work as a Scalar or Vector?

  Is work a vector or a scalar quantity?

• Problem 2: Negative Work Scenarios

  Can work be negative? If so, in what cases does it occur?

• Problem 3: When is Energy Not Conserved?

  In what cases is mechanical energy not conserved?

• Problem 4: Work Done on a Box

  A box weighing 900 [N] rests on the ground. Calculate the work required to move it at a constant speed:

  • a) Moving Horizontally Against Friction

    4 [m] on the floor against a friction

Photogrammetry and Imaging Fundamentals

• Photography is a complete representation of an object that provides metric information. False.
• Photogrammetry allows us to reconstruct a three-dimensional model from a photograph of an object. False.
• To perform photogrammetric restitution, it is necessary to orient photographs to their position at the time of the shot. True.
• A photogrammetric document provides qualitative exploitation. True.
• Photogrammetry is a method suitable for small tracts of land. False.
• To perform photogrammetric restitution, it is necessary to have a photograph of the object to be restituted. False.
• The ideal photogrammetric camera is one that allows the continuous and accurate capture of an image. False.

Camera and Image Quality

• The aerial

Types of Motion

Uniform Rectilinear Motion (MRU)

The MRU definition is that the velocity vector remains constant. That is, the speed is constant in magnitude and direction.

Uniformly Accelerated Rectilinear Motion (MRUA)

The MRUA is motion where a body travels on a straight line maintaining a constant acceleration.

Uniform Circular Motion (UCM)

Uniform Circular Motion (UCM) is one in which a mobile describes a circle with constant angular velocity.

Uniformly Accelerated Circular Motion (UCMA)

Uniformly Accelerated Circular Motion (UCMA) is one in which the mobile moves in a circle with constant angular acceleration.

Fundamental Principles of Dynamics

Newton's Laws of Motion

First Law (Law of Inertia)

A body remains in its state of rest or Uniform Circular... Continue reading "Fundamental Concepts of Classical Mechanics and Energy" »