Notes, abstracts, papers, exams and problems of Physics

Heat Transfer

Heat is the transfer of energy from one part of a body to another, or between bodies that are at different temperatures. Heat is energy in transit and always flows from hotter bodies to those with a smaller temperature. Temperature is the quantity that tells us how hot or cold an object is in comparison with a reference.

Temperature Scales

• Celsius: The most used international unit for ordinary temperature measurements.
• Fahrenheit: The temperature unit proposed by Gabriel Fahrenheit, which is fixed at zero and one hundred for the freezing and boiling temperatures of ammonium chloride in water, respectively.
• Kelvin: The temperature unit scale established by William Thomson, based on the degree Celsius, with the absolute zero point set

Report N° 2: Physics Laboratory II

Electric Field and Potential

Concepción, April 13, 2009

Members:

• Carla Cáceres
• Jorge Gonzalez
• Fabián Soto

Teacher:

• Alberto Inostroza

Assistant:

• Raul Augurto

Objectives

• Determine how to map electric potential in a plane and draw equipotential lines.
• Derive the form of the electric field charge distribution in the plane from the equipotential lines diagram.

Materials

• Graph paper
• Glass cuvette
• Cables
• Voltmeter
• Multimeter
• Water
• Support

Setup

After verifying the materials were in good condition, the work platform was assembled. The glass cuvette was filled with approximately 3-4 mm of water. A sheet of graph paper was placed beneath the cuvette, aligned so that the gridlines were straight. Using the support, the positive and negative... Continue reading "Electric Field and Potential: A Physics Lab Report" »

Material Testing: Hardness, Toughness, Fatigue, and Creep

Hardness Testing

Static Methods

• Brinell: A steel ball indenter is used, and the area of the footprint is measured. Suitable for metals.
• Vickers: Employs a pyramidal indenter tip with a square base. The surface of the print is measured. Prints are comparable regardless of the load. Applicable to any material (soft or hard), and thin pieces can be measured with small loads. Surface hardness can also be measured.
• Rockwell: Uses either a steel ball (Rockwell B) or a diamond cone (Rockwell C) penetrator. Measures the depth of the trace. Offers universal application and direct reading.

Dynamic Methods

• Poldi Method
• Rebound (Shore or Hammer Scleroscope)

Toughness Testing

Toughness is the work or energy... Continue reading "Material Testing Methods: Hardness, Toughness, Fatigue, Creep" »

St. Peter's Colonnade

Building System

Arquitravat

Dimensions

15m high columns

Elements

Colonnade supporting an entablature surmounted by a balustrade and statues.

Interior Space

Bernini's design addressed several challenges:

1. Protocol: Accommodating a large number of pilgrims.
2. Topography: Working with uneven terrain.
3. Visibility: Creating a space that didn't obstruct the view of the basilica or surrounding palaces.
4. Focal Point: Integrating the Egyptian obelisk as the square's centerpiece.
5. Symbolism: Imbuing the square with significance as a symbol of the Church.

Bernini's solution involved a two-part design: two straight, slightly converging arms leading to an elliptical space centered around the obelisk and flanked by fountains. The portico comprises four... Continue reading "St. Peter's Colonnade: Architectural Masterpiece" »

Irradiance

This is the power emitted by the body per unit area and wavelength (W · nm^-1 • cm^-2). Furthermore, the irradiance of a lamp that is showing is similar to a black body.

Emissivity

It is the ratio of the irradiance of the lamp and a black body at the same temperature:

Emissivity (e, t) = I (lamp) (E, T) / I (black body) (E, T).

Gray Body

This occurs when the emissivity is independent of the wavelength of the lamp in question.

Deuterium Lamp

It is a low-pressure lamp that has a smooth continuum between 200 and 400 nm, and from this last value, the spectrum is more irregular with a large number of peaks. It also has a life of a few hundred hours. The QTH lamp (quartz-tungsten-halogen) issues more visible light than the Deuterium lamp in the... Continue reading "Spectrophotometry Basics" »

Average Speed

The average speed of a moving object is the ratio of the distance traveled along its path to the time taken.

Average speed = Δs / Δt

In vector calculus, the average velocity vector of a moving object is the ratio of its displacement vector to the time taken.

v = Δr / Δt

Instantaneous Velocity

The instantaneous velocity of a body is its velocity at a specific point in its trajectory. Its magnitude is called speed.

Acceleration

Acceleration measures how much the velocity of an object changes per unit time. Since velocity is a vector, changes can affect its magnitude, direction, or both.

Average Acceleration

The average acceleration of an object over a time interval is the change in its velocity divided by the time interval.

a = (v - v₀)... Continue reading "Understanding Kinematics: Speed, Velocity, and Acceleration" »

Diffraction Grating Experiment

Subject:

Calculate the d-spacing (d) of diffraction grating and determine wavelengths of different light sources.

Planning:

A diffraction grating is an optical component that separates light into its constituent wavelengths. There are two main types of diffraction gratings: reflection gratings and transmission gratings. A diffraction grating consists of a surface with a series of closely spaced parallel lines or slits. These can be etched onto a flat metal surface (reflection grating) or a glass plate (transmission grating). When monochromatic light (light of a single wavelength) is incident on a diffraction grating, the emerging waves interfere constructively at specific angles, resulting in a pattern of constructive... Continue reading "Diffraction Grating Experiment: Calculating Wavelengths" »

Content

Labor Force, Kinetic Energy, Potential Energy, Conservative and Nonconservative Forces, Power.

Development

Labor Force

A constant force produces work when applied to a body, it moves along a certain distance.
While work is done on the body, there is a transfer of energy to it, so it can be said that work is energy in motion. Moreover, if a constant force produces no movement, no work is done. For example, holding a book at arm's length does not involve any work on the book, regardless of effort. Work is expressed in Joules (J).

When the force is in the direction of motion:

L = Fd

L: Work done by force.

When the applied force has an inclination with respect to movement:

L = Fd cos θ

All the forces perpendicular... Continue reading "Work, Energy, and Power in Physics: Understanding the Basics" »