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# Physics

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## Shaminder Chhina

on 6 January 2014

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#### Transcript of Physics

Fields
Magnetic Fields
Electric Fields
Gravitational Fields
A field is a physical quantity that has a value for each point in space and time. Some examples of fields include gravitational fields, magnetic fields, and electric fields
Magnets and Magnetism
What are Magnets
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.
The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces. The local strength of magnetism in a material is measured by its magnetization.
Law of Magnetic Poles
The law of magnetic poles is a law which states that like poles of magnets repel each other, and unlike poles attract each other
Domain theory of Magnetism
The domain theory is a theory about magnetism forces and it's properties. The theory states that a magnet is made up of very small regions (atoms) whereby, magnetic forces occur as a result of these atoms aligned to face the same direction. The theory is used to explain where magnetic forces come from in a magnet.
These atomic magnets, or dipoles, interact with their nearest neighbouring dipoles and a group of them line up with their magnetic axes in the same direction to form a magnetic domain
The region of magnetic force around a magnet is called a magnetic field and is represented by magnetic field lines that show the direction of the force on the N-pole of a small test compass at each point in the
field.
Planets magnetic field
Planet's have magnetic fields that help to keep the planet stable and helps in its rotation
For example, Earth has a magnetic field causes a tilt in its axis and causes the magnetic field to constantly shift
The magnetic field of the Earth deflects most of the solar wind. The charged particles in the solar wind would strip away the ozone layer, which protects the Earth from harmful ultraviolet rays. It also helps to figure out the direction as a compass uses these magnetic fields to point the direction
Magnetic Fields
What is a magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field.
Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin.
This equations helps to determine the magnetic force and is called Lorentz Force Law where; q represents the charge of the particle in coulombs, v represents the velocity, and B repersents the magnitude of the magnetic field where Theta is the angle < 180 degrees between the velocity and the magnetic field. This implies that the magnetic force on a stationary charge or a charge moving parallel to the magnetic field is zero.
F = qvB Sin Theta
Describing Magnetic Fields
Magnetic forces between two poles followed an inverse-square law of the same form as that describing the forces between electric charges. The law states that the force of attraction or repulsion between two magnetic poles is directly proportional to the product of the strengths of the poles and inversely proportional to the square of the distance between them.
Magnetic fields are continuous and unbroken, in which they begin on the north pole and terminate on the south pole
Mathematical Example
Question: A small piece of space debris enters the earth's atmosphere and reacts with the earth's magnetic field/ Of the earth's magnetic field is 5.0x10-5 T and the debris is traveling at a speed of 280 m/s, gaining a charge of 200. If the debris enters at a 90 degree angle towards the magnetic field, what is the force of magnetism in this case.

Solution:

q= 200C
v= 280 m/s
B= 5.0x10-5 T
Theta (angle)= 90 degrees

F_M= qvBsin Theta
F_M=(200C)(280m/s)( 5.0x10-5 T)(Sin90 degrees)
F_M= 2.8 N

Therefore, the force of magnetism acting on the debris is 2.8 N.

Applications and technology
Magnetic Fields have many applications in the real world. Some Examples include:
CERN
CERN is an international organization whose purpose is to operate the world's largest particle physics laboratory.
CERN's main function is to provide the particle accelerators and other infrastructure needed for high-energy physics research – as a result, numerous experiments have been constructed at CERN following international collaborations.
CERN consists of a proton synchrotron. This is a type of particle accelerator that uses magnetic fields sending protons sending it in a spiral to gain energy and shooting it out when it have gotten enough energy.
The magnets in the synchrotron bounce of particles and deflect them.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body.
Magnetic resonance imaging (MRI) is done for many reasons. It is used to find problems such as tumors, bleeding, injury, blood vessel diseases, or infection. MRI also may be done to provide more information about a problem seen on an X-ray, ultrasound scan, or CT scan
A strong magnetic field is created by passing an electric current through the wire loops. While this is happening, other coils in the magnet send and receive radio waves. This triggers protons in the body to align themselves. Once aligned, radio waves are absorbed by the protons, which stimulate spinning. Energy is released after "exciting" the molecules, which in turn emits energy signals that are picked up by the coil. The final product is a 3-D image representation of the area being examined.
Metal Detectors
In a metal detector, pulses are sent to determine the location of a metal object. A pulse is sent into the coils which creates a magnetic field.

This creates an electrical spike and should any metallic item come in contact with the field, the electrical spike will last longer and create an echo, which gives the machine the location
Environment and Society
In our society, the usage of magnetic fields has a large impact on how we work. Some examples include:
Health
Technology such as MRI's are extremely important to the health of the people as they allow doctors to scan the patients body and determine what the problem is and what possible solution can be determined
However, frequent use of MRI's can cause harm to the individual as these machines are not to be used on a regular basis
Environmental Impact
Mining has a large impact on the environment as digging through the earth and looking for precious minerals is harmful to the environment.

Magnetic fields provide for less harmful ways of mining as metal detectors, an application of magnetic fields, provide more effective mining operations and less negative environment impact
Electricity
What is Electricity?
Electricity a form of energy resulting from the existence of charged particles (such as electrons or protons), either statically as an accumulation of charge or dynamically as a current. Electricity is the flow of moving electrons. When the electrons flow it is called an electrical current.
In electricity, charges produce electromagnetic fields which act on other charges.

The law of electric charge states that opposite charges attract and like charges repel
Coulomb's Law
Coulomb's law or Coulomb's inverse-square law is a law of physics describing the electrostatic interaction between electrically charged particles.
This equation helps to determine the magnitude and direction between two electric forces
The variables shown represent:

F= the force between two electrical forces
k= coulombs constant, 9.0 x 10^9 N • m2 / C2
Q1= Magnitude of first charge
Q2= Magnitude of second charge
d= distance between the centers of the charges
Mathematical Example for coulombs law
Problem: Suppose that two point charges, each with the charge of +2.00 coulombs are separated by a distance of 3 meters. determine the magnitude of the electrical force of repulsion between them.

Solution:

Q1= 2.00 Coulombs
Q2= 2.00 Coulombs
d= 3 meters
F=?
F=(k•Q1•Q2)/d^2
F=((9.0x10^9 )•(2.00)•(2.00))/(3^2)
F=4x10^9 N

Electric Potential
Electric potential energy is the energy stored in a system of charges separated by "r" distance
The electric potential at a point is equal to the electric potential energy (measured in joules) of any charged particle at that location divided by the charge (measured in coulombs) of the particle.
Electric Potential Equation
Electric Potential Energy Equation
PE = kQq/r
Electric Fields
What is a electric field
An electric field is generated by electrically charged particles and time-varying magnetic fields. The electric field describes the electric force experienced by a motionless positively electrically charged test particle at any point in space relative to the source(s) of the field.
The concept of an electric field was introduced by Michael Faraday in the 19th century. Electric fields start on positive charges and ened on negative charges. The lines diverge and spread apart from positive point charges to negative point charges.
Objects with an stronger electric charge create stronger fields. the density of the lines reveals the strength of the field.
Equation for an electric field
The equation for an electric field is a vector and is represented by the following equation:
E= F/Q
E= Electric field strength

F= Force experienced by the test charge

Q= the quantity of charge
A positive charge exerts out and a negative charge exerts in equally to all directions; it is symetric. Field lines are drawn to show the direction and strength of field. The closer the lines are, the stronger the force acts on an object. If the lines are further each other, the strength of force acting on a object is weaker.
Science Behind Magnetic Fields
Applications and societal and environmental impacts
Point Charge
A point charge is a charged entity which occupies a single minute point (ideal condition) in space. So, for practical purposes, we can consider any tiny charged body as a point charge.
Point Charge can be repersented by the equation:
E= kQ/r^2
E= electric field strength
k=coulombs constant
r= distance from center of sphere
Q= the charge of the sphere
Mathematical Example
Problem: What is the electric field strength 0.82 m away from a sphere with a positive charge of 1.5x10^-8 Coulombs.
Solution:
E=?
Q=1.5x10^-8 C
r= 0.82 m
k= 9.0x10^9

E= kQ/r^2
E= (9.0X10^9)(1.5X10^-8)/(0.82^2)
E= 2x10^2 N/C [Outwards]

Therefore, the electric field strength is 2x10^2 N/C [Outwards]
Science of Electric Fields
Applications and societal and environmental impacts
Applications and Technology
CERN for electrical fields
CERN also uses aspects of electric fields to function.
CERN is a collection of particle accelerators that send a proton through beams to increase its energy. However, there needs to be a source from where they collect these protons.

The source of these protons is a bottle of hydrogen. By using an electric field, the electrons are pulled away from the hydrogen atoms leaving a proton.
Pacemakers
A pacemaker is a small device that's placed in the chest or abdomen to help control abnormal heart rhythms. This device uses electrical pulses to prompt the heart to beat at a normal rate.
The pacemaker monitors the heart beat and when there is no beat within a certain time limit, the pacemaker provides a electrical signal that causes the heart to beat
The Electrical fields provide those who have irregular heartbeats the opportunity to keep their heart functioning properly
Metal Detectors
Like Magnetic fields, electric fields are crucial in the usage of metal detectors.
There are two parts of the metal detector coil, the inner and outer coil. The outer coil has electricity running through it in alternating directions which creates a electromagnetic field
The inner coil amplifies and picks up frequencies from metal objects
Environment and Society
Electric Fields provide many benefits as it gives society new ways of harvesting energy and is also crucial for the environment, and our economy.
Environmental Impact
Economic Impact
Electricity is one of the most important aspects for a country as it provides energy
All forms of electricity generation have some level of environmental impact. Most of the electricity in the United States is generated from fossil fuels, such as coal, natural gas, and oil.
Using energy more efficiently through more efficient end-uses or through more efficient generation, such as combined heat and power, reduces the amount of fuel required to produce a unit of energy output and reduces the corresponding emissions of pollutants and greenhouse gases.
Electric Fields provide for electricity, which is a very crucial resource in our society.
Being a crucial resource, the use of electricity provides for many jobs, and also gives consumers a better standard of living
Electricity provides us with inventions that boost the economy and provides more job oppertunities, which keeps the economy flowing
What is Gravity?
Gravity
Gravity is the natural force of attraction exerted by a celestial body, such as Earth, upon objects at or near its surface, tending to draw them toward the center of the body.
The more matter, the more gravity, so things that have a lot of matter such as planets and moons and stars pull more strongly.In addition to depending on the amount of mass, gravity also depends on how far you are from something. This is why we are stuck to the surface of the Earth instead of being pulled off into the Sun, which has many more times the gravity of the Earth.
Gravity is what gives you weight. It is the force that pulls on all of the mass in your body.
Earth's Gravitational Fields
The gravity of Earth, denoted g, refers to the acceleration that the Earth imparts to objects on or near its surface.
It has an approximate value of 9.81 m/s2, which means that, ignoring the effects of air resistance, the speed of an object falling freely near the Earth's surface will increase by about 9.81 metres (32.2 ft) per second every second.
Gravity is responsible for holding people and other matter on the earth's surface. Gravity also keeps the moon and other satellites in their orbits around the Earth
Gravitational Fields
What is a gravitational field?
A gravitational field is the region of space surrounding a body in which another body experiences a force of gravitational attraction.
The closer one object is to another, the stronger the gravitational field. In the Solar System, planets that are closer to the Sun have a much stronger force of attraction acting on them.
The strength of a gravitational field is proportional to the mass of of the central body and the distance from the central body
Force of Gravity equation
Where:

F(g)= the force of gravity in newtons
G= Gravitational constant (6.67x10^-11)
m=mass of object in kg
r=distance from centers
This equation helps to determine the strength of the gravitational field of an object and the force of gravity in between objects.
Mathematical Example
Question: A meteor is flying past the earth and is coming as close as 300 thousand kilometers towards earth. The asteroid has a mass of 35.678x10^18 kg. If the earth has a mass of 5.972x10^24, what is the force of gravity when the meteor is at its closest.

Solution:

G= 6.67X10^-11
m1= 35.678x10^18 kg
m2= 5.972x10^24
r= 300,000 km or 3.0x10^8 m

F(g)=(Gm1m2)/r^2
F(g)=(6.67x10^(-11) (35.678x10^18)(5.972x10^24))/(3.0x10^8)^2
F(g)=1.579x10^17 N

Therefore, the force of gravity between the earth and the meteor is 1.579x10^17 N.

Application and technology
Gravitational fields are used very often and have many technological uses. Some major uses include satellites and mining exploration.
Satellites
A satellite is an artificial body placed in orbit around the earth or moon or another planet in order to collect information or for communication. Satellites are one of the application uses of gravitational fields
GPS
Stands for global positioning system. A GPS helps to find the location and give directions to other destinations
There are 28 operational GPS satellites surrounding the earth.
GPS's are able to triangulate your location using three GPS satellites to narrow down and find your location.
Cellular and satellite phones
Cellphones are used very frequently and is one of the most used device used on the planet. Cellphones rely on cellular towers whereas satellite phones rely on satellites orbiting the planet.
These phones are different as sat phones are used less frequency due to cellphones being less expensive and more simple to use. Sat phones are used in areas in which there are no cellular towers.
Mining using Satellite imagery
With the help of satellites, scientists have been able to determine how to look for minerals. By using thermal and infrared cameras, they can locate mineral deposits
By using satellites this way, this reduces the environmental damage and preserves the natural state of an economy
The science of gravitational fields
Societal and environmental impact
Gravity constantly effects the environment in terms of tidal waves and generating hydroelectricity. This provides clean energy and helps the enviornment as well as society.
Tides
Tidal waves come from the moons gravity are constantly effected by it
The moon is able to use its gravity in order to pull the ocean which creates tides.
This is extremely important as the usage of tidal generators is able to create clean, renewable energy, which reduces the effect on the environment. These tides provide society with clean energy that is not harmful to the environment, unlike fossil fuels.
Hydroelectricity
Hydroelectricity uses the ocean current in order to generate electricity which creates clean energy.
Hydroelectricity uses the gravitational potential energy of the ocean to generate this energy. Some examples include the Hoover Dam in the U.S and Niagara Falls, which has hydroelectric generators that use the falls to generate electricity
Hoover Dam
Hydroelectric Generator diagram
Physics (SPH4U0)
By: Shaminder Chhina

References
How does electricity affect the environment?. (2013, September 25). Retrieved from http://www.epa.gov/cleanenergy/energy-and-you/affect/