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

Level Instruments Based on Electrical Characteristics

Conductive or Resistive Meter

This instrument consists of a probe with two electrodes. When the tip of the electrodes contacts a conductive liquid, it closes an electrical circuit. An amplifier unit then switches a meter contact.

Applications: These serve as level switches for conductive liquids in containers, provided the liquids are not excessively viscous or corrosive.

Ultrasonic Level Meter

This meter uses tunable, high-frequency sound waves that propagate through the gas phase until they collide with the liquid or solid surface.

Usage:

• As an alarm level indicator: The frequency is damped when the liquid wets the sensors.
• As a continuous level indicator: The emitted signal reflects off the liquid/

Gravitational Force

Gravitational force is the fundamental force of attraction that exists between any two objects with mass. It causes the acceleration experienced by an object in the vicinity of a planet or satellite. Due to gravity, we feel weight. If an object is on a planet and not under the influence of other forces, it will experience an acceleration directed approximately towards the center of the planet. It is also known as gravity, gravitational pull, or gravitational interaction.

Weight

Weight is a force. The force exerted on bodies due to gravity is known as body weight. The weight of a body is proportional to its mass; i.e., the higher the body's mass, the greater its weight.

Spring Tide

These are the tides that occur during the full... Continue reading "Physics Fundamentals: Understanding Forces and Tides" »

Measurement Process Analysis

Measurement, regardless of the magnitude, involves decisions on:

Measurand

The measurand is of fundamental importance to the choice of instrument.

Measure or Check

Measure determines the numerical value of a quantity, while verification confirms if a magnitude is within preset limits.

Geometric Characteristics of the Scale

1. Provision of Space to Measure

• Exterior
• Interior
• Depth
• Distance

2. Geometric Shape

2.1 Form of Isolated Elements

• Straightness
• Roundness
• Form a line
• Flatness
• Cylindrical
• Form a surface

2.2 Guidance of Isolated Elements

• Parallelism
• Perpendicularity
• Angularity

2.3 Positioning of Associated Elements

• Position of an element
• Concentricity
• Symmetry
• Circular
• Total

Logistical Difficulties

Part size, specimen weight, mobility, measuring... Continue reading "Measurement Process Analysis: Principles and Techniques" »

Radio Frequency Carrier and Amplitude Modulation

The **RF carrier** is shown with its amplitude varying according to the frequency and amplitude of the modulating signal. In AM radio, the audio *sidebands* have a different bandwidth than the carrier. Regulations often limit the maximum audio frequency to 15 kHz.

Handling Variable Audio Signals

Question: What to do if the audio signal is variable?

Answer: Varying the amplitude of the carrier in time with the audio signal (Amplitude Modulation).

Antennas: Definition and Function

An antenna is a device designed for the purpose of transmitting or receiving electromagnetic waves in space. A transmitting antenna transforms electromagnetic wave voltages into radiated waves, and a receiving antenna performs... Continue reading "Fundamentals of RF Carriers, Modulation, and Antenna Technology" »

Understanding Magnetic Force

The fundamental principle behind all magnetic phenomena is that a force arises between electric charges when they are in motion. This force is known as magnetic force.

Key Discoveries and Experiments

Oersted's Discovery (1820)

In 1820, Hans Christian Oersted accidentally discovered that an electric current could produce a magnetic field, deflecting the needle of a compass.

Faraday's Power Line (1831)

Michael Faraday's concept of the 'power line' explained the behavior of forces acting at a distance.

Properties of Magnetic Field Lines

The properties of magnetic field lines are:

1. All magnetic field lines run from the north to the south magnetic pole.
2. The magnetic field strength is directly proportional to the number of field

Standing Waves & Speed of Sound: Experimental Analysis

Purpose of the Experiment

• To investigate the relationship between the frequency of vibration and tension in waves on a vibrating string.
• To measure the speed of sound experimentally.

Part 1: Standing Waves on a Vibrating String

Procedure for Part 1

• Vary the tension on the string by hanging different weights at its ends. Use 150g, 200g, and 250g.
• Once a standing wave is achieved, record the following information in a table: mass, weight (tension) on the string, frequency, wavelength, wave speed, and the square root of the tension.
• Relevant formulas: λ = 2L / n, f = 1 / T (where T is the period), v = λf, and v = √(T / μ).
• Create a graph of wave speed (v) versus the square root of the tension

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:

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