Assignment 1 SPRING 2018 Assignment 1 Date: 22-Februray-2018 Instructor: Dr. Mohammed Abdul Majid Course: Introduction to Electromagnetic Fields ECE170 (1) Renad alLagani S14106772ECE 170 Assignment 1 Instructor: Dr. Mohammed Abdul Majid 1.
Writ a clearly-written, understandable paper about the applications (most recent) of devices working on electromagnetics principle. Rules: • Every student (or group of 3) is expected to write minimum 10 applications • Include at least 10 references The paper will be graded using the following rubrics: Paper Content: Introduction (20%) Physical Concept (Theory) (40%) Diagram explaining the application(s) (20%) References (10%)1 Writ a clearly written, understandable paper about the applications (most recent) of devices working on electromagnetics principle It was only until the 19th century when electricity and magnetism were unified to bring about the new phenomenon of electromagnetism by the physicist Hans Chrisitan Oersted (1777-1851) 8. He revealed how an electric current flowing in a conducting material produces a magnetic field 9. As a result, many advanced technological devices were introduced since then such as the CD player, doorbell, electric motor, power drill, hairdryer, electric mixer, electric saw, and radio; all of which exhibit electromagnetic properties 7. Three significant electromagnetic devices branching from different fields will be discussed in detail further on. The first electromagnetic device to be discussed has witnessed a great impact in the spectrum of medicine, that is the MRI machine found in hospitals.
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MRI stands for Magnetic Resonance Imaging, and it utilizes electromagnetism to scan the patient’s body in order to obtain pictures revealing the inside of his body 2. The purpose of using MRI includes illness diagnosis, treatment monitoring, and also pregnancy inspection 2. Unlike X-rays, MRI does not expose patients to ionizing radiation making it less risky than X-rays 3. However, It brings about strong forces due to the powerful magnetic field it exhibits 3. That is why patients with medical implants, usually containing metal, are not allowed 3.
Although MRI is expensive to build, images generated are clearer in contrast to images produced by X-rays or Computed Tomography. The functionality of the MRI lays upon a physical core concept that is Electromagnetism. The reason why this is applicable on human beings is because water molecules constitute a major part of Typical structure of an MRI 13 Spin –up 12 Spin –down 122 the body, and a water molecule consists of an oxygen atom with two Hydrogen atoms such that Hydrogen nuclei (protons) posses strong nuclear magnetic resonance that respond to the induced magnetic field changes. Protons spin in two different ways either spin-up or spin-down where the magnetic dipole moment points in a direction relative to the rotation of the proton.
The energies of protons spinning up and down cancel each other to yield a net of zero. Going back to MRI, its structure consists of a large magnetic machine where a bed can slide through. Two main attributes of the magnetic machine is its magnetic field and radiofrequency pulse, both of which have a certain role to accomplish. The external magnetic coils direct a constant and uniform magnetic field that creates a torque on the protons tending to align the dipole moment along the axis parallel to the magnetic field lines, also known as the procession axis. However due to the angular momentum, the magnetic dipole moment will keep rotating about the procession axis. The oscillating radiofrequency pulse perpendicular to the magnetic field is directed onto the protons to cause flattened procession. Pulse at a certain frequency prompts protons to gain enough energy to change from a low-spin to a high-spin state.
Hence, all protons will be spinning in the same direction. Post this transition and after turning off the magnetic field, protons return to their original state while releasing photons of energy that correspond to different intensities making up an image. Note that the higher density of Hydrogen corresponds to a higher intensity. This variation in intensity is what shapes the visual content of a MRI image. Electromagnetism is the secret behind the development of a MRI machine.
1 Secondly is the Maglev Train, a recent electromagnetic-based transportation system. Maglev is short for Magnetic Levitation, and it is an advanced speed train that uses electromagnetics to move. It is much faster than the traditional train, such that its speed is more than 500kp 4. In fact, Japan lately broke the world record demonstrating a Maglev high-speed rail that transports with a speed of over 600kph 5.
Another great aspect of Maglev trains is that there is no energy lost in friction between the wheels and rail since the Maglev does not have wheels in the first place due to levitation 6. Hence it eliminates out noise pollution that was usually due to friction of wheels on rail 6. However, weather (snow, rain, or hail) won’t be a problem since the train is hovering above ground 6. Besides the many advantages of Maglev trains, current railway infrastructure is not compatible with Maglev trains 10. Thus a new set up starting from zero is required to implement them.3 Maglev trains make use of the basic principle of Magnetism that is like poles repel and different poles attract with regard to dipole materials 4. Maglev trains employ three different sets of electromagnets to achieve three functions: Levitation, Propulsion and Guidance 6.
Metal coils line the guideway of the railway track, in which repel the large magnets fixed on the underside of the train causing it to levitate or float 1 to 10 cm above track 5. This is how levitation is achieved specifically by electromagnetic suspension. However, it’s unstable at very high speed such that it’s difficult to maintain a constant distance between the train and track 6. Nevertheless, levitation can be achieved by an alternative method using the repulsive force of superconducting magnets. They are stable at high speed but complex and costly 6. Yet, levitation via any method results minimal resistance to zero friction between railway and bottom of train.
To achieve the function of propulsion, coils with dipole characteristics line the sides of the train and walls of the guideway. Power is supplied to the guidway electromagnets such that polarity constantly alternates to allow a series of push and pulls on the train 4. In other words, the magnetic field in front of the train is pulled forward, while the magnetic field at the back of the train is pushed forward 4. Another set of magnets is used for guidance, keeping the train centered over the guideway 6.
Together levitation, propulsion and Levitation and Propulsion of Maglev Trains 14 Electromagnetic Suspension 15 Electrodynamic Suspension 154 guidance are what establish the functionality of maglev trains. A third electromagnetic device is a recent invention by the NASA, the POINTER. POINTER stands for “Precision Outdoor and Indoor Navigation and Tracking for Emergency Responders”, or in simple words it’s a tracking device for firefighters 11. Due to steel and concrete buildings it became difficult to track emergency responders, because GPS and radio waves cannot penetrate walls or even travel underground 11. However, this type of communication is limited to outdoor navigation. Unfortunately, many tragedies occurred where emergency responders suffocated to death by smoke because they couldn’t find their way out in time 11. Hence, NASA took it as their mission to find a solution to this.
Thankfully, they thought of electromagnetic fields that have non-line of sight capabilities, such that steel and concrete walls won’t be a problem anymore 11. They installed an electromagnetic field transmitter in a backpack, so that signals propagate to reach the receiver outdoors with tracking data 11. In spite of its short-range communication, it has rewarding attributes.
For instance, it can track in space instead of just a two dimensional plane 11. In addition, it can determine the different orientations of the device 11. The study and research in this area is still in progress, in fact they plan to shrink the size of the device to the size of a plan, and then to the size of a button 11. In conclusion, the area of electromagnetic fields had a major impact on our daily lives. It dragged many advanced technologies with it, three of which were discussed earlier: MRI, Maglev Trains, and POINTER. Hopefully, more electromagnetic devices are yet to be invented and discovered.
POINTER receiver 16 POINTER transmitter 165 Bibliography: 1"Magnetic Resonance Imaging (MRI)", YouTube, 2014. Online. Available: https://www.youtube.com/watch?v=rJ9gV4yFMi8. Accessed: 22- Feb- 2018. 2R. (ACR), "Body MRI – magnetic resonance imaging of the chest, abdomen and pelvis", Radiologyinfo.
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Accessed: 22- Feb- 2018. 13Researchgate.net. Online. Available: https://www.researchgate.net/profile/Heather_Haynes/publication/266266309/figure/fig1/AS:[email protected]/Schematic-diagram-of-an-MRI-machine-illustrating-the-concentric-arrangement-of-coils.
png. Accessed: 22- Feb- 2018. 14C. Wilkins, "How Maglev Works", Energy.gov, 2016. Online.
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