Electromagnetism
Ellis Ruan
But pretty much every other phenomenon that happens on scales between those two depends on electromagnetism. Most obvious are the two from which the force derives its name: electricity and magnetism. These were the subject of much investigation and experimentation by 19th century physicists such as Michael Faraday and James Clerk Maxwell. It was Maxwell who in the 1860s showed that electricity and magnetism are in fact two aspects of one unified phenomenon: moving electric currents caused magnetic fields, and magnetic fields induce electric currents to flow. Maxwell also showed in his classical theory of electromagnetism that electric and magnetic fields always propagated at the same constant speed: the speed of light, c.
Electromagnetism manifests as both electric fields and magnetic fields. Both fields are simply different aspects of electromagnetism, and hence are intrinsically related. Thus, a changing electric field generates a magnetic field; conversely a changing magnetic field generates an electric field. This effect is called electromagnetic induction, and is the basis of operation for electrical generators, induction motors, and transformers. Mathematically speaking, magnetic fields and electric fields are convertible with relative motion as a four vector.
Electromagnetism is a fundamental concept in physics and is essential for understanding many other scientific principles. Classical mechanics, which deals with the motion of objects, is built upon the laws of electromagnetism. Therefore, a strong foundation in electromagnetism is necessary for a deeper understanding of classical mechanics.
It can be challenging to learn electromagnetism before classical mechanics, as it requires a solid understanding of basic mathematical concepts such as calculus and vector algebra. However, with dedication and practice, it is certainly achievable.
To improve your understanding of electromagnetism before classical mechanics, it is crucial to have a strong foundation in mathematics and to practice solving problems. It can also be helpful to read textbooks and watch online lectures to supplement your learning. Additionally, seeking guidance from a mentor or joining a study group can also aid in understanding difficult concepts.
Metamaterials are rationally designed man-made structures composed of functional building blocks that are densely packed into an effective (crystalline) material. While metamaterials are mostly associated with negative refractive indices and invisibility cloaking in electromagnetism or optics, the deceptively simple metamaterial concept also applies to rather different areas such as thermodynamics, classical mechanics (including elastostatics, acoustics, fluid dynamics and elastodynamics), and, in principle, also to quantum mechanics. We review the basic concepts, analogies and differences to electromagnetism, and give an overview on the current state of the art regarding theory and experiment-all from the viewpoint of an experimentalist. This review includes homogeneous metamaterials as well as intentionally inhomogeneous metamaterial architectures designed by coordinate-transformation-based approaches analogous to transformation optics. Examples are laminates, transient thermal cloaks, thermal concentrators and inverters, 'space-coiling' metamaterials, anisotropic acoustic metamaterials, acoustic free-space and carpet cloaks, cloaks for gravitational surface waves, auxetic mechanical metamaterials, pentamode metamaterials ('meta-liquids'), mechanical metamaterials with negative dynamic mass density, negative dynamic bulk modulus, or negative phase velocity, seismic metamaterials, cloaks for flexural waves in thin plates and three-dimensional elastostatic cloaks.
This core physics course deals with classical electromagnetism. This course includes considerations of: electrostatic fields in free space and in dielectrics; magnetic fields due to steady and varying currents; electromagnetic induction; magnetic materials and Maxwell's equations. The course includes a lab component as part of the combined second year lab program; designed to introduce lab techniques, data analysis and learn physics that is not covered in the course workshops.
Without an adequate theoretical understanding of electromagnetism it was difficult to fix technological problems such as the overheating of telegraph wires, or the distortion of signals over long distances.
But no-one had been able to develop an adequate theory that combined all these separate laws of electricity and magnetism into a whole. Such a theory would not only summarise known experimental results but would also give new insights into how electricity and magnetism combined to produce electromagnetism.
Although Faraday worked in chemistry and discovered benzene, his greatest discoveries involved electricity. He experimented with electromagnetism and found that moving a magnet through a loop of wire would electrify the wire. In 1821, he invented the electric motor, and in 1831 he made the first dynamo, known as the Faraday disc, a forerunner of today's electrical generator, when he discovered the induction of electric currents. Faraday's law of induction is the basic operating principle of transformers and many types of electrical motors and generators.
He discovered the "Faraday effect," the first evidence that light and electromagnetism are related. He also discovered electrolysis, the use of electricity to separate matter. In addition to the dynamo, he invented the "Faraday cage," a device that blocked electric waves.
Electricity and magnetism are very closely related. The study of both, and how they are connected, is called electromagnetism. This page is just a brief introduction to electromagnetism, and contains information you may find useful for Science Buddies projects. There are entire textbooks written about electromagnetism, though; this is just the beginning!
An electric current is nothing more than moving electric charges. Anytime an electric charge moves, a magnetic field is created. You might wonder if moving magnets (or a changing magnetic field) would create an electric current or get electric charges to move. The answer is yes, it can. This aspect of electromagnetism is often used to create electricity in electric generators. You can learn more about the link between electromagnetism and generating electricity in some of the hands-on projects linked below.
As you noticed from my question. I am willing to do a Ph.D. in electronic/electromagnetism engineering. I am very interested in the topic of electromagnetism and its application. I love everything that has to do with Maxwell equations.
The answer probably depends on what you want the degree for. Although grad school can be fun and rewarding, the point of a PhD is ultimately to learn how to conduct original research in your field and (just as importantly) to find a future job doing that original research. Unfortunately, it's extremely difficult to have a research-oriented career outside of academia (although this varies with the field in question), and getting an academic career involves--- regardless of your talent and skill and determination--- being extraordinarily lucky; it's not something you can get just by working hard enough or wanting it enough. Fortunately, if you're mainly interested in working with and studying electromagnetism, there are avenues for doing so outside of getting a PhD that won't tax your health.
How does the imagination work? How can it lead to both reverie and scientific insight? In this book, Kieran M. Murphy sheds new light on these perennial questions by showing how they have been closely tied to the history of electromagnetism.
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