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# Physics: Fields (electrical, magnetic and gravitational)

fields
by

## Tarandeep Sidiura

on 16 April 2011

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#### Transcript of Physics: Fields (electrical, magnetic and gravitational)

MAGNETIC FIELDS FIELDS GRAVITATIONAL FIELDS ELECTRIC
FIELDS Motion of Charged Particle in Electric Field A charged particle will move in a uniform motion if the electric field in which it passes is also uniform. This relationsip can be represented by

As a result, the charged particle moves with uniform acceleration, through a vaccum with negligible effects of gravity A change in the particles kinetic energy will produce a equivalent change to the particles potential energy Electrical Potential Electrical Potential Energy is the energy stored in system of two charges that are certain distance (r) apart from eachother. Represented by the following:

Where,
k = Coulomb's Constant
q1 and q2 = charge of spheres
r = distance between two spheres
Ee= Electrical potential energy Electrical Potential Difference is the amount of work required per unit charge to move a positive charge from one point to another in an electrical field, it is the difference in electrical protentials between two points. The electrical potential energy is independient from the path taken.

Where,
Ee= Change in Electrical potential
q = electrical charge
V= Potential differernce between points A and B Electrical Potential (V) is the value in volts of potential energy per unit positive charge; where 1V =1J/C. This property illustrates the amont of force needed to move a positive test from rest to a particular point in the field of q1

Where,
V= Electrical Potential
K= Coulomb's constant
q1=Charge of sphere
r= The distance between the test charge and q1 Negative Electrical Potential Positive Electrical Potential Applications of Electric Fields Electrophoresis A science application of electric fields which utilizes the fact that many large molecules in the body are charged, and can be moved in the pressence of electrical fields. The different molecules will move at different speeds due to differences in mass and charge. It is the main process in molecular seperation and can be used to study the DNA bands of family members. The benefits of electrophoresis include faster diagnosis of blood disorders such as sickle cell anemia. As well as to identify various genetic disorders caused due to defects in the DNA sequence. STSE CONNECTIONS
Society: Provides citizens with a method of determining which type of medical research needs funding. The testing also allows families to begin to save money for medical expenses if they know a family member is at risk of a genetic/Medical disorder
Technology: Provides the basis for further developments in DNA analysis, by showing medical professional how DNA molecules react in a electric field
Environment: Help scientists examine DNA of various plants and see why certain plants are successful in different habitats. Then use that knowledge to try and create plants that will be very effiecient in helping to reduce greenhouse gases
Science: Allows scienctists to discover new illnesses and find cures for exsisting diseases Electrostatic
Precipitators A application of electric charges and fields which utilizes these principals to benefit the enviroment and human health. The benefits of this include a reduction in air pollution that creates smog in big cities, which has many negaive health effects on human health, especially targeting the resiratory system. Also, the soot, ash and dust collected from the process can be used to make concrete which can help reduce costs of construction and help society. The emmissons are passed through serveral positively chagred plates in the device, along with negativly charged wires. The machine ionizes the surrounding air, the wire has a large enough negative charge. The electrons freed from this will attach to air contaminants making them negativly charged, and they will be atracted to positive plates, preventing them from being released into the environment. They are air cleaning devices used mainly in factories to clean the emmisons being released. The Electrostatic Precipitor reduces air pollution by removing about 99% of particles which include soot, ash, and dust Electrocardiogram The understanding of electrical potential differences, has allowed medicine to monitor electrical activity of the heart Benefits
Monitor heart activity to discover abnormal heart activty which is an indicator heart problems. Used to detect and treat heart attacks A ECG detects the changes in electrical potential as created by neuron which produce electrical fields that effect electrical protential differences in the heart STSE CONNECTIONS
Society: The ECG testing done by doctors allows people to become aware of how their lifestyle is affecting their heart. It will allow societies to adopt a more healthy lifestyle and increase the life expectancy of individuals
Technology: No significant connections
Enviroment: In order to eat healthy to help their heart, people will begin to farm and eat fruits and vegetables, which can help reduce CO2 from the atmosphere as plants use CO2 for energy production
Science: The ECG allows medical professionals to understand the impacts of daily life and exercise on the heart, such as stress and tension Inkjet Printers A application of physics in technology and society, that has become a houshold requirment over the last few years Benefits
It has allowed society to move forward, and use technology as a main method of communication compared to hand writing, making it more neat and readable. It controls ink droplets directed towards thee paper using charged parallel plates. When the printer comes to a place that is not to be printed on, the charging electrode is turned on producing an electric field. This prevents the drops from reachign the paper, but instead go to the gutter to be used later. STSE CONNECTIONS
SOCIETY: It allows individuals communicate more effectivly and neatly
ENVIRONMENT: It is damaging to the environment because in order to print we need paper. For this purpose lots trees are cut down detorying many habitats
History ROBERT MILIKAN March 22nd, 1868 one of the most
respected physicist was born His Experiment... Robert Milikan was able to accuratly determine the chargeof an electron. Using tiny, charged oil drops, which he then balanced, measured the volatage and dropped it one at a time with gravity. By measuring its terminal speed and recording it, he determiend that total charge had a difference of a very small value. Small Value = ELEMENTRY CHARGE e = 1.602x10E-19 C Example Question Electric Forces: Coulomb's Law Developed by French Physicist
Charles Augustin de Coulomb in1785 The force between two point charges is inversely proportional to the square of the distance between the charges and directly proportional to the product of the charges States that the relationship between two charge, indicating the force of repulsion or attraction depending on the charge of the spheres
Link with Newtons Law... Follows Newtons Third Law, where the electric force exerted on both spheres is equal in magnitude and oppostite in direction. When Does it Apply??? When the charge on the spheres are extremly small, and the spheres are smaller then the distance between them. The Equation... Where...
F = Magnitude of the force of repulsion (or attraction) in Newtons (N)
r = Distance between two spheres
k =
q1 and q2 = electric charge of sphere in Coulomb (C) REFERENCES Measuring Magnetic Fields Applications of Magnetic Fields Charged Particle in Magnetic Field Right Hand Rules Earth's Magnetic Fields The Domain of Magentism Effects of Magnetic Fields Properties of Magnetic Fields The Law of Magnetic Poles States that moving electric charges produce a magnetic field Principal of Electromagentism Describes in terms of tiny homoheneous regions called domains, how material can be magnetized; where each domain mimics a bar magnet Domain Theory Ferromagnetic substances are made of many tiny regions known as domains. These domains are in a random orientation preventing the object from being magnetized These domains can be aligned bya strong magnet, making the object magnetic; these are Induced Magnets States that opposite magnetic poles will attract while similar poles will repel eachother. A pole is a region at the end of a magnetized body where the magnetic attraction is the greatest The magnitude of the magnetic force on a charged particle is:

1. proportional to the magnitude of magnetic field , the velocity , and charge on particle

2. Dependent on angel between magnetic field and velocity Where,
F = magnitude of the force on the moving charged particle
q = charge of particle
v = velocity
B= magintude of magnectic field The direction of the magnetic force can be determined using the right hand rule as follows: Magnetic Field of a Current Loop A current loop will produce a magentic field where each segment produces its won field similar to a sraight conductor, but will combine to make a 3D field similar to a bar magnet Using your right hand wrap your fringers in the direction of the current, and your thumb will point to the north side of the magnetic field Right Hand Rule for Current Loop The field lines will be produced when the electric current flows through a straight conductor, producing magentic field lines which are concentric to the conductor Magnetic Field of a Stright Conductor Right Hand Rule for a Straight Conductor Grasp the conductor in the right hand, and point the thumb in the direaction of the current. The curled fingers point in the direction of the magnetic field lines Magnetic Field of a Coil or Selenoid A selenoid is a long conductor that is made into a coil, where the magnetic field of a coil is the sum of the magnetic fields of all its loops. The field inside the coil is very strong Right Hand Rule for a Solenoid Grab the coil in your right hand, with you fingers pointing in the direction of the current flow. The thumb will point in the direction of the magnetic field lines in the core. Since the magnitude of the force on the charged particle is always perpendicular to the velocity, it indicates that it will only change direction of the velocity. A positively charged particle in a magnetic field perpendicular to its velocity will move in a constant speed through a uniform magnetic field in a circular path Sir William Gilbert, a notable english physicist created a model to describe the earth's magnetism He stated that the earths magentic field, is like a bar magnet placed in the middle of the earth in alignment with the axis The magentic field of earth is 3D, as it has a horizontal, vertical and a dimension between the two called the Magnetic Inclination Benefits
It protects us from the harmful effects of solar winds and solar flares produced by the sun. However in the process it gets stretched In a non-uniform magnetic field the magnitude will increase in the direaction of the motion. The force on the electrons will decrease because of the magnetic field, causing it to spiral reversly producing a magnetic mirror A magnetic mirror occurs when the field becomes stronger than the direction of the motion of the particle, which slows the motion. 1. They all have the same strength 2. They flow from south to north pole within a material, and from north to south in air 3. They are the most dense near the poles 4. They look for a path with minimum resistance between opposite magnetic poles Example Question The Yamato 1 Fingerprinting MAGLEV Train MRI Machines Earth's Magnetic Field This ship uses the principals of magentic fields to propel the ship. It uses the magnetohydrodynamic (MHD) propulsion system. It uses a large superconducting magnet to produce a strong magnetic field, after which it uses two parallel plates to create large potential difference. The potential difference creates a current in the seawater perpendicular to the magnetic field. This causes the seawater to be pushed out of the back of the motor pushing the motor forward using newtons third law of motion, that action force will have a reaction force equal in magnitude and opposite in direction. STSE Connections
Society: It is an inexpensive alternative to convential motors, more affordable for most people
Technology: No production of greenhouse gases, since there is no internal combustion
Environment: No production of greenhouse gases, since there is no internal combustion. Helps keep the planet. No propellors which save fish from being killed or disturbed, also no noise produced, perserving the ocean habitats
Science: Will allow scientists to produce alternative engines for vehicles and planes by exploring magnetic technologies
The law of magnets have helped detectives uncover fingerprints at crime scenes The newly developed fingerprint powder allows detectives to retrieve fingerprints that were once impossible due to conventional methods. The powder is made up of fine iron flakes that are designed to attach to the greasy residue left behind by fingerprints. The excess it removed using a magnet, limiting the risk of destroying the print due to contact STSE Connections
Society: A safer community, as law officials will be able to arrest criminal much faster with stronger evidence
The magnetic resonance imaging (MRI) scanners use the principals of magentic fields and apply that to the field of medicine The MRI scanner uses a superconducting magnet, which as the ability to produce a very large and stable electric field. This magnetic field is created using several coils of wire though which electrical current flows. The magnetic field affects the body's atoms, forcing the nuclei into a different position. As they move back into place they send out radio waves of their own. The scanner picks up these signals and a computer turns them into a picture. These pictures are based on the location and strength of the incoming signals.

STSE Connections
Society: No risk of radiation exposure like other medical machines, allows doctors to diagnose diseases that were once impossible to detect
Environment: Does not use medical isotopes which emit radiation and can harm the environment
Science: Uses the principals of magnets with medical knowledge to These trains use electromagnetic forces to leviate the cars on the tracks. This done by using series of magnets on the cars themselves and on the tracks. Using those magnets, the train acheives motion through the law of magnets where similar poles repel and opposites attract. To slow down, the attraction and respulion are opposite to the direction of motion STSE Connections
Society: Train is able to travel much faster then convential trains, allowing people to travel faster, and reach their destinations more conveniently
Environment:The high speeds may attract more people to use the train instead of cars, helping to reduce greenhouse emmisions and save the planet. Also does not use coal or fossil fuel, and is again helping the einvrionment
Technology: It uses magnets to replace conventional wheels on a train, allowing transportation methods to progress. It is natural applicaication of electric fields, it helps to protect us from the dangerous solar winds produced by the sun which are really radioactive. Keeps us alive, because without it, the solar winds or flares could strip out planets atomosphere. Example Question Law of Universal Gravitation The law of universal gravitation applies to all bodies in our solar system The Universal Law of Gravitation states that exert a gravitational force of attraction on each other. The magnitude of the force is proportional to the product of the gravitational masses of the objects, and inversely proportional to the square of the distance between them Sir Isaac Newton was born on December 25 1642, and he is known to be one of the greatest physicists The story of his discovery is that he was drinkign tea and during that time he observed an apple fall from a tree. Due to that apple Newton concluded that the same force that caused the apple to fall is responsible for making the moon orbit the earth Applications of Gravitational Fields Satellites In order for a satellite to be successful, we must understand gravity. To launch a satellite into space you must know how much thrust will be needed for the rocket carrying the satellite will need to overcome earths garvity and enter space. Once in space understanding earth graivational field and the force of gravity will be cruical for the satellite to remain in orbit. STSE Connections
Society: Help people navigate with the aid of Global positioning Systems (GPS)
Technology: The military uses satillites for surrvalence and monitoring
Environment: It is used to track storms, and natural disasters Roller Coasters These fast paced, adrenaline pumping rides are an important part of society, and it uses the principals of gravity to operate. In order for the roller cost to work to work, it is usually brought up to high point on the track building gravitational potential energy. Once it reaches the top, the carts are released, causing the gravitational potential energy to be transformed in kinetic energy. The roller coaster uses gravity to accelerate and increase its speed to a point that it can complete the course. Gravitational Fields Exists in the space surrounding an object in which the force of gravity exists Gravitational Field Strengths on Earth By: Tarandeep Sidiura STSE connections
Environment: Helps reduce the number of pollutants in the air. Helps to minimize the contributions to the greenhouse effect by factories
Society: By reducing air pollution it helps people with respiratory disease
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