Magnetic fields are a little different. They only push on moving charges, and they push more on charges that are moving faster. But they do not push at all on charges that are sitting still. However, a changing magnetic field can produce an electric field, and an electric field can push on any charges. This idea, called electromagnetic induction, is used to make electric generators, induction motors, and transformers work. Together, electric and magnetic fields make up the electromagnetic field.
Before 1800, people thought that electricity and magnetism were two different things. However, this changed during the 19th century when scientists like Hans Christian Ørsted and Michael Faraday proved that electricity and magnetism are actually connected. In 1820, Ørsted found that when he turned the electric current from a battery on and off, it moved the needle on a nearby compass. When he studied this effect more carefully, he discovered that the electric current was producing a magnetic field. That is, when electric charges are moving, they can produce a force that pushes on magnets. Ørsted had found one of the first connections between electricity and magnetism.
Faraday continued studying this connection, running tests with loops of wire and magnets. He found that if he set up two loops of wire and ran electricity through just one of them, he could (for a little while) produce an electric current in the other loop as well. Faraday also discovered that he could produce a current by moving a magnet through a loop of wire, or by moving the wire over a magnet. What Faraday had shown was that magnets could push back on moving electric charges, and that moving magnets could push on charges sitting still. This was like what Ørsted had found, but in reverse.
in 1873, James Clerk Maxwell summed up these connections in his theory of "classical electromagnetism," electricity and magnetism together. This theory was based on a set of four equations called Maxwell's equations, and the Lorentz force law. Maxwell's equations told us how to relate electricity and magnetism. They said that charges sitting still could push on other charges, but moving charges could produce magnetic fields that push on magnets. On the other hand, magnets sitting still can only push on moving charges, but moving magnets can push on any electric charges.
What's more, Maxwell's studies showed that light could be described as a ripple in the electromagnetic field. That is, light moves like a wave. However, Maxwell's work did not agree with classical mechanics, the description of forces and motion originally developed by Newton. Maxwell's equations predicted that light always moves through empty space at the same speed. This was a problem because in classical mechanics, velocities are "additive"-- if a person A on a train moving at speed X throws a ball with speed Y, then a person B on the ground sees the ball moving with speed X+Y. According to Maxwell, if person A turns on a flashlight, they will see the light moving away from them at speed "c". But person B on the ground must also see the light moving at speed "c", not "c"+X. This led to the development of the theory of special relativity by Einstein, which explained how the speed of light could be the same for everyone, and why classical mechanics does not work for things moving very fast.
Albert Einstein's work with the photoelectric effect and Max Planck's work with blackbody radiation did not work with the traditional view of light as a continuous wave. This problem would be solved after the development of quantum mechanics in 1925. This development led to the development of quantum electrodynamics which was developed by Richard Feynman and Julian Schwinger. Quantum electrodynamics was able to describe the interactions particles in detail.
Electromagnetic radiation is thought to be both a particle and a wave. This is because it sometimes acts like a particle and sometimes acts like a wave. To make things easier we can think of an electromagnetic wave as a stream of photons (symbol γ).
A photon is an elementary particle, meaning that it cannot be broken down into smaller particles. It is the particle that light is made up of. Photons also make up all other types of electromagnetic radiation such as gamma rays, X-rays, and UV rays. The idea of photons was thought up by Einstein. Using his theory for the photoelectric effect, Einstein said that light existed in small "packets" or parcels which he called photons.
Photons have energy and momentum. When two charged objects push or pull on each other, they send photons back and forth. So photons carry the electromagnetic force between charged objects. Photons are also known as messenger particles in physics because these particles often carry messages between objects. Photons send messages saying "come closer" or "go away" depending on the charges of the objects that are being looked at. If a force exists while time passes, then photons are being exchanged during that time.
Fundamental electromagnetic interactions occur between any two particles that have an electric charge. These interactions involve the exchange or production of photons. Thus, photons are the carrier particles of electromagnetic interactions.
Electromagnetic decay processes can often be recognized by the fact that they produce one or more photons (also known as gamma rays). They proceed less rapidly than strong decay processes with comparable mass differences, but more rapidly than comparable weak decays.
Acton, Massachusetts
Acton is a town in the U.S. state of Massachusetts. It is 21 miles away from Boston.
Urbana, Illinois
Urbana is a city in the U.S. state of Illinois. It is the twin city of Champaign, Illinois and is separated by a single street. The main campus of the University of Illinois is in Urbana and Champaign. As of 2019, it has population of 42,214.
Population (2010) • City 41,250
Bill Oddie
William Edgar (Bill) Oddie OBE (born 7 July 1941) is a British comedian, actor, writer and television personality.
Oddie was born in Rochdale, Lancashire and grew up in Birmingham. He read English Literature at Pembroke College, Cambridge where he gained an MA. He is most famous for his birdwatching and conservation work. In the 1970s, he was a member of the BBC One television comedy series, The Goodies. Doctors found that his mother, Lilian, had schizophrenia. Oddie says that he does not remember her living at home because she spent a lot of her life in mental hospitals.
Oddie has bipolar disorder.
Montgomery Ward
Montgomery Ward was an American department store chain. It currently exists only as an online retail website since 2004. It only delivers in the United States.
It started as a mail-order catalog (called a "Wish Book") and department store in 1872. It owned Jefferson Ward discount stores. Jefferson Ward stores in the northern US were sold to Bradlees in 1985. The rest closed in 1988. All its stores closed in 2000. In 2004, it reopened as an online store.
Montgomery Ward was founded by Aaron Montgomery Ward, a Chicago entrepreneur.
Toe
Toes are the "digits" of the foot of an animal. Many animal species walk on their toes, and are called "digitigrade". Humans, and other animals that walk on the soles of their feet, are "plantigrade"; hoofed animals are "unguligrade".
In humans, the bones of each toe continue all the way to the heel, although in from the base of the toes they come together in the body of the foot. The inside toe is by far the thickest, and is called the "big toe", "great toe", or "hallux".
The one on the other end is short and thin. The toes, especially the big toe, play an essential role in walking, although a loss of the smallest toe will not affect the way people move.
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