INTRODUCTION
Physics is the science of nature. Study the properties of matter, energy, time, space and their interactions. Hence a wide range of fields and natural phenomena, from subatomic particles to the formation and evolution of the Universe as well as a multitude of everyday natural phenomena.
For your study, physics can be divided into two main branches, Classical Physics and Modern Physics. The first is responsible for the study of those phenomena that have a relatively small speed compared to the speed of light and whose spatial scales are much larger than the size of atoms and molecules. The second is in charge of phenomena that occur at the speed of light or values close to it or whose spatial scales are of the order of the size of the atom or less and was developed from the 20th century.
Within the field of study of Classical Physics are:
- Mechanics Thermodynamics Mechanical Waves Optics Electromagnetism: Electricity - Magnetism
Within the field of study of Modern Physics are:
- Relativity Quantum Mechanics: Atom - Nucleus - Chemical Physics - Solid State Physics Particle Physics
Experiment No. 1 Water Density (Performed by I. Tovar)
Necessary material
- 3 large glasses, an egg, water, salt
Process
- Fill two glasses with water. Add salt to one of them little by little. Stirring with a spoon, try to dissolve as much as possible. In a 200 cm3 glass, about 70 g of salt can be dissolved.Place the egg in the glass that has only water: it will go to the bottom.Now place it in the glass in which you have dissolved the salt: you will observe how it is floating. the egg and water until it covers it and a little more, in the third glass. Add salt water, which you already have, until you get the egg between two waters (it neither floats nor sinks).If you add a little water at this time, you will see that it sinks. If you add some of the salt water next, you'll see it float again. If you add water again, it will sink again and so on.
Explanation
Two forces act on the egg, its weight (the force with which it is attracted to the Earth) and the thrust (the force that the water makes upwards).
If the weight is greater than the thrust, the egg sinks. Otherwise it floats and if they are the same, it is between two waters.
The thrust that a body undergoes in a liquid depends on three factors:
- The density of the liquid The volume of the body that is submerged The gravity
By adding salt to the water, we get a denser liquid than pure water, which makes the thrust of the egg greater and exceeds the weight of the egg: the egg floats.
This can also explain the fact that it is easier to float in sea water than in river and pool water.
Applied law : The law of gravitation, first formulated by the British physicist Isaac Newton in 1684, states that the gravitational attraction between two bodies is directly proportional to the product of the masses of both bodies and inversely proportional to the square of the between them. Algebraically, the law is expressed as F = G m1 m2
Density is defined as the ratio between the mass of a body and the volume it occupies. Thus, as in SI, mass is measured in kilograms (kg) and volume in cubic meters (m3), density is measured in kilograms per cubic meter (kg / m3). This unit of measurement, however, is very little used, as it is too small. For water, for example, since a kilogram occupies a volume of one liter, that is, 0.001 m3, the density will be:
Most substances have densities similar to those of water, so if you were to use this unit you would always be using very large numbers. To avoid this, another unit of measurement is usually used: the gram per cubic centimeter (gr./cc), so the density of the water will be:
Density measurements are, for the most part, now much smaller and easier to use. In addition, to go from one unit to another, simply multiply or divide by a thousand.
The density of a body is related to its buoyancy, one substance will float on another if its density is less. That is why wood floats on water and lead sinks in it, because lead has a higher density than water, while the density of wood is lower, but both substances will sink in gasoline, which has a lower density.
Density: Density is a characteristic of each substance. We are going to refer to homogeneous liquids and solids. Its density practically does not change with pressure and temperature; while gases are very sensitive to variations in these magnitudes.
Experiment No. 2 Conductivity (Carried out by JL Guevara)
ELECTROLYTE
Liquid medium (Dissolution / Conductivity)
Conductivity in liquid media is related to the presence of salts in solution, the dissociation of which generates positive and negative ions capable of transporting electrical energy if the liquid is subjected to an electric field. These ionic conductors are called electrolytes or electrolytic conductors.
Conductivity determinations are called conductometric determinations.
These determinations have many applications, such as: in the industrial area la, since the consumption of electrical energy in electrolysis depends largely on it, in laboratory studies to determine the salt content of various solutions during water evaporation (for example in boiler water or in the production of condensed milk) or also the basicities of the acids can be determined by conductivity measurements, to determine the solubilities of poorly soluble electrolytes and to find concentrations of electrolytes in solutions by titration.
The basis of the solubility determinations is that poorly soluble saturated electrolyte solutions can be considered as infinitely diluted. By measuring the specific conductivity of such a solution and calculating the equivalent conductivity according to it, the concentration of the electrolyte is found, that is, its solubility.
An extremely important practical method is that of conductometric titration, that is, determining the concentration of an electrolyte in solution by measuring its conductivity during the titration. This method is especially valuable for cloudy or heavily colored solutions that often cannot be titrated using indicators.
The structure of a good number of solid substances is maintained due to the balance between the set of attractive and repulsive electrostatic forces that exist between the ions of which they are formed. These charges maintain their position and the body appears electrically neutral.
If we connect it between two points of a circuit, the current will not circulate.
In order to give mobility to these charges, the solid structure must disappear and, therefore, the bonds between the ions must be broken. If we increase its temperature, the melting point will be reached, and thus, the body loads, now liquid, will enjoy freedom of movement. Similarly, if we dissolve a portion of solid in a suitable liquid, ions from it will be free to move inside the solvent. The bodies that carry out these processes of production of free charges in liquids are called electrolytes and, in addition to ionic components, they can be acids, salts, hydroxides…
DRIVING IN LIQUIDS
An electric field established in an electrolytic solution will act on the free charges and will produce a joint displacement of them, so that we will be able to detect the passage of current through the liquid. The electrodes used in an electrolytic cell are called anode (+) and cathode (-), and must be chemically inactive; the most used are platinum threads.
Once the field is established, the negatively charged ions will slowly move towards the anode, which is why they are called anions. The positively charged ions (cations) will be directed in the opposite direction, that is, towards the cathode. Thus, a double current will be produced.
Often when a cation reaches the cathode, it receives from it one or more electrons coming from the external circuit, while the anions can give over to the anode those electrons that are left over to remain electrically neutral.
As early as 1833, Michael Faraday observed that pure water is insulating, but dissolutions of certain substances in water are not. If two electrodes connected to the terminals of a direct current generator are inserted into a glass with distilled water, we will not see a current flow. It will be enough to dissolve small amounts of salt or sulfuric acid so that we have the opportunity to observe a certain intensity of electric current.
The phenomenon of conduction of electric current through a liquid is called electrolysis and is accompanied by certain chemical effects. If the dissolved electrolyte contains metal cations, metal deposition can occur at the cathode, using suitable electrodes.
Electrostatic Experiment No. 3. (Performed by M. Barrera)
Electrostatic Principle
Category of physical phenomena originated by the existence of electrical charges and by their interaction. When an electric charge is stationary, or static, it produces electrical forces on the other charges located in the same region of space; when in motion, it also produces magnetic effects. The electrical and magnetic effects depend on the relative position and motion of the charged particles. When it comes to electrical effects, these particles can be neutral, positive, or negative. Electricity deals with positively charged particles, like protons, that repel each other, and negatively charged particles, like electrons, that also repel each other. Instead, the negative and positive particles attract each other.This behavior can be summarized by saying that charges of the same sign repel and charges of different sign attract.
Experiment
Van Der Graaff Generator (VDG)
Patented in the USA in 1929 with the number US1991236
How does it work?
The motor spins the rubber. It goes around the glass and steals electrons from it. The rubber band is bigger than the glass tube. The electrons stolen from the glass are distributed throughout the rubber band. The positive charge on the glass draws electrons from the wire into the top brush. These electrons charge the air leaving the brush tips. The air is repelled by the wire and drawn to the glass. But the charged air cannot get to the glass, because the rubber band gets in the way. The charged air reaches the rubber and transfers electrons to it. The rubber band reaches the brush below. The electrons in the rubber push the electrons in the wire. The electrons in the cable are pulled away and go to ground or to the person holding the cable.The tips of the lower brush are now positive and they pull the electrons from any air molecule that touches them. These positively charged molecules are repelled by the wire with the same charge and are attracted to the electrons in the rubber. When they reach it, it picks up its electrons again, and the rubber and air lose their charge.
The rubber band is now ready to steal more electrons from the glass tube. The brush above is connected to the can of soda. It has a positive charge and attracts electrons from the can, the positive charges from the can move away from each other.
Electrons are transferred from the soda can to ground, using the rubber band for this. In a short time the can of soda loses so many electrons that it becomes 12,000 volts more positive than the ground connection. If the can were larger, a higher voltage would be reached. Air is ionized in an electric field of about 50,000 volts per centimeter. Ionized air conducts electricity like a cable. You can see ionized air conducting electricity when it gets so hot that it emits light, in this case we call it an electric spark.
Author-Robert Van Der Graaff
Biography
Van de Graaff was born in Tuscaloosa, Alabama. Tuscaloosa is a city in west central Alabama, on the Black Warrior River in Tuscaloosa County. The Tuscaloosa County seat6, is the fifth-largest city in the state with a population of 79,294 (U 2003.S. Census Bureau Estimate). The city occupies a single location on the Black River Fall Line of the warrior on the border between the Appalachian mountain and the coastal plain of the gulf approximately 311 kilometers. He was the designer of the Van Generator Van de Graaff. The generator is a machine that uses a moving belt to accumulate very high loads in a hollow metal balloon. The potential differences achieved in Graaff Generators Modern Van can be up to 5 megavolts.Applications for high voltage generators exist with high voltage x-ray tubes, food sterilization, and nuclear physics experiments, a device that produces high voltage which constitutes high voltage depends on the situation and the field of science or the industry involved. Laypeople generally considers the pipes of the house to be of high voltage largely because they are dangerous and the highest voltage that they normally find.Laypeople generally considers the pipes of the house to be of high voltage largely because they are dangerous and the highest voltage that they normally find.Laypeople generally considers the pipes of the house to be of high voltage largely because they are dangerous and the highest voltage that they normally find.
The International Electrotechnical Commission defines high voltage as more than 1000 V, low voltage as above 50 V but below 1000 V, and additional low voltage (ELV) as below 50 V. In 1929, Van de Graaff developed his first generator (which produces 80,000 volts) at Princeton University from Princeton University, located in Princeton, New Jersey, is the fourth oldest institution of higher education in the United States. Often considered one of the nation's top universities, Princeton has, in addition to its student university and graduate school, schools of architecture, engineering, and public and international affairs. He was a national research Companion,and from 1931 to 1934 a research associate in the Massachusetts Institute of Technology Massachusetts Institute of Technology, or MIT, is a research and educational institution located in the city of Cambridge, Massachusetts, the USA MIT is a leader of the world in science and technology, as well as in many systems of engineering, management, economics, linguistics, political science, and philosophy.
Among his most prominent departments and schools are the Lincoln Laboratory, the Computer Science and Artificial Intelligence Laboratory, the MIT Media Laboratory, the Whitehead Institute and the MIT Sloan School of Management. He became an associate professor in 1934 (remaining there until 1960). During World War II, Van de Graaff was director of the high-voltage radiographic project. After World War II, he co-founded the High Voltage Engineering Corporation (HVEC). During the 1950s, he invented the core isolating transformer (producing high-voltage direct current). He also developed tandem generator technology. The American Physical Society awarded him the T. Bonner Prize (1966) for the development of electrostatic accelerators. Van de Graaff died in Boston,Massachusetts Boston is the capital and largest city of the Commonwealth of Massachusetts in the United States. The city is also the county seat of Suffolk County. It is the unofficial capital of the region known as New England as well as one of the oldest and richest cities in the United States, with an economy in line with education, health care, finance, and high technology.
Formulas
The triboelectric series
The most positive ones
(at this end they lose electrons)
- AsbestosRabbit hairGlassHairNylonWoolSilkPaperCottonHard rubberSynthetic rubberPolyesterPlastoformOrlonSaranPolyurethanePolyethylenePolypropylenePolyvinyl chloride (PVC tube) TeflonSilicone rubber
The most negative
(at this end they steal electrons)
materials
- An empty can of soda A small nail A large rubber band 1 to 2 cm wide and 6 to 10 cm long A fuse about 5 × 20 millimeters A small direct current motor (from a toy) A glass of plastoform (or waxed paper) Instant glue Two cables about 15 cm long Two pieces of plastic pipe 3/4 inch PVC 5 or 7 cm length 3/4 PVC coupling One 3/4 T connector PVC Adhesive tape One block of wood
Flowchart
Experiment No. 4 Transmissibility (Carried out by Gabriel Morante)
High voltage motor
An electric charge creates an electric field around it. If the charge moves, it also produces a magnetic field. It is also known that every electric charge that moves within a magnetic field experiences a force. In other words, if you have two mobile electrical charges, they are not only subjected to the electrostatic forces that are mutually exerted due to their charge, but also that other electromagnetic forces act between them, depending on the values of the charges and the velocities of these. In a region of space a magnetic field will be said to exist when a moving charge penetrates a force that depends on the velocity of the charge.
Like electric fields, magnetic fields can be materialized by lines of force, which can take different forms, depending on the agent that creates the field.
As we can see in the previous photograph, it is the magnetic field created by a magnet, the lines of force leave a sona of the same called the north pole and return to another area that is called the south pole. And it is in the vicinity of these poles where the lines of force are tightest and, as a consequence, where the greatest intensity is manifested by magnetic phenomena.
Just as in an electric field, and for similar reasons, the lines of force of a magnetic field are continuous lines that do not intersect each other.
The force acting on a positive charge q, which moves within a magnetic field, perpendicular to the lines of force and with a speed (v), depends on the value of the charge, its speed and a specific characteristic of the field, called magnetic induction.
Magnetic induction of a field, at a point in it, is the force acting on a unit of positive charge that moves, perpendicular to the lines of force, with a unit of speed. Which is represented by B.
If on a positive charge q, which moves perpendicular to the lines d force of a magnetic field with a speed v, a force F acts, the magnetic induction of the field, that is, the force acting on each unit of charge and by unit of speed, is determined by the formula:
Since magnetic induction is the coefficient that results from dividing a force between the product of a charge by a speed, its dimensional formula is obtained by operating with the dimensional formulas of each of these magnitudes:
The magnetic induction unit in the international system is called a tesla. "Tesla is the induction of a magnetic field in which a coulomb charge moving perpendicular to the force lines with a velocity of 1 m / s is subjected to a force of one Newton." It is represented by T.
Knowing a bit about the theory, let's start the high voltage motor experiment, in which we can see some of the applications of magnetic induction.
Material:
- 2 aluminum cans (for soda or beer) 1 disposable plate 1 disposable cup 1 pen 1 meter of aluminum foil 2 clips silicone pistol adhesive tape 2 connectors or wires with lizard tip Puma cutter (30cm)
Step 1
We can start by smearing glue on the glass, to be able to stick a piece of aluminum foil to the glass.
Once the aluminum has been glued to the glass, we will cut two strips of the glued aluminum, each strip should measure about half an inch. Taking into account that they should not touch each other.
Step 2
We will cut one end of the cougar, placing it in the center of the base in order to have more friction or movement of the base.
Step 3
We must place the pen in the center of our plate sticking it with the silicone
Step 4
We will glue the two cans on the same plate, giving rise to the glass so that it can have its rotation. As shown in the previous photo.
Step 5
To each can, with the adhesive tape, we will place the clips, so that they can rub against the glass.
Step 6
Now we take the wire, placing it in the right can and the other end to an aluminum sheet placing it on the monitor or on the screen of a television.
The other cable or wire we will fix it in any place where we generate earth, it could be a part of the computer.
How will it work?
Once the aluminum foil is placed on the monitor, we must turn on the television to attract it and give the release of electrons, and thus be able to turn the glass.
Experiment No. 5 Internal Energy Storage (Carried out by Dario Magallanes)
INCLINED PLANE
Objects sliding or rolling down an inclined plane are used to illustrate friction and moment of inertia.
MATERIALS
- Smooth and straight board at least 1 meter long Blocks of various materials Various cylinders and spheres
PROCESS
Blocks of various materials are placed on the plane (one by one or simultaneously), and the plane is raised to an angle where the block only begins to slide. The angle is illustrated to be different for different materials such as wood or plastic. Show that for a given material, the critical angle is independent of the object's mass and contact area. Show that the angle at which an object begins to slip is slightly greater than the angle required to continue sliding once the object is in motion.
With the plane tilted at a fixed angle, roll cylinders, spheres, and rings down from it. Before doing this, ask the audience which will get to the bottom faster. Repeat the operation with objects of different size and same mass, and of equal mass and different mass. Show that if the plane is tilted too steep the objects will slide rather than roll.
Compare the speed of an object rolling without slipping and one sliding without friction (simulated with a high-mass object with small wheels). Both cases conserve mechanical energy, but the sliding object touches the bottom before the other rolls because all of the initial potential energy is converted to translational energy without any being lost in rotation.
ANALYSIS
Friction exerts a force in the opposite direction to the direction in which something is moving or trying to move. The friction force is proportional to the normal force, which in this case is a component of the gravitational force on the object in a direction perpendicular to the plane. If the inclined plane is inclined at an angle (Theta) with respect to the horizontal so that the object slides or is about to slide, the friction force is directed upward in the plane and has the magnitude of friction is directed up in the plane and it has the magnitude of
Where W is the weight of the object, and µ is the coefficient of friction. The amount µ is typically in the range of 0.01 to 1.0 and depends on the material and the condition (roughness) of the surfaces but not the contact area. The coefficient of friction depends somewhat on the speed of the object and, in particular, is greater when an object is at rest (static friction) than when it is in motion (kinetic friction).
The block will start to slide as soon as the component of gravity in the direction of the plane (W sin (theta)) is equal to the friction force, then
Independent of the weight W. The measure of the critical angle (θ) at which the block begins to slide then gives us a measure of the coefficient of friction. Friction converts the block's potential energy into the inclined plane into heat as the block slides downhill so that it can reach the bottom without potential energy or very little kinetic energy.
RISKS
There are no risks in this demonstration except making sure that when objects reach the bottom of the inclined plane, they are caught or stopped to prevent any collision damage.
Illustrations:
Experiment No. 6 Friction and Moment of Inertia (Performed by Esmeralda Perales)
The returning tin.
A can, when rolled on the table, reaches a point where it is at rest and then returns, illustrating the concept of internal energy storage.
MATERIALS
- Cylindrical tin with removable lid (opaque) Elastic band Weighs with a hole in the center
PROCESS
The can is constructed with the elastic band tied through its center and passing from one side to the other of the cylinder and the weight hanging from the band in the center so that when the can rolls the band can wrap itself. The can reaches a resting point and then returns to where it started. It may appear that the table is not level, but the can can be rolled in any direction and the result is the same. It helps to rotate the rat once or twice before releasing it to compensate for loss of friction when rolling. A can lid should be easily removable to reveal its contents and explain the operation.
ANALYSIS
This demonstration illustrates the conversion of kinetic energy to potential energy and vice versa. Potential energy is stored internally in the rolled elastic band. Similar comparisons can be made by winding a watch, filling the car with gasoline, the energy stored in atoms and molecules, and the energy of the mass itself.
From the point of view of relativity theory, the mass of the can and its internal mechanism increases slightly as the elastic band winds up, and it is this increase in mass that is converted into kinetic energy when the can starts to roll from rest. One can estimate the change in mass
To show how this is normally detectable in slow traveling objects compared to the speed of light. For example, if the can had an initial velocity of 1 m / s, the fractional increase in its mass would be less than
RISKS
There are no significant risks in this demo.
Illustrations.
Inside of the Can:
You can see the cylindrical shape of the can and in a transparent view of it you can see the elastic band (red) with the weight (black) in the center of it.
Can movement when rolling.
- It begins to roll, the band twists and stores potential energy The can stops, reaches a state of rest The potential energy is transformed into kinetic energy when the elastic band uncoils, the can returns to the point where it started to roll
BIBLIOGRAPHY
Network resources:
- www.scitoys.comwww google.comwww.monografias.comwww.wikipedia.comhttp: //encyclopedia.thefreedictionary.com/ (Robert Van Der Graaff)
Encyclopedias:
- Encarta 2004 Ocean Encyclopedia Visual Atlas Encyclopedia
Books:
- TL Liem, Invitations to Science Inquiry, Ginn Press: Lexington, Massachusetts (1981).JP VanCleave, Teaching the Fun of Physics, Prentice Hall Press: New York (1985).JS Miller, Physics Fun and Demonstrations, Central Scientific Company: Chicago (1974).
