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Magnetic field may refer to: Current (I) flowing through a wire produces a magnetic field (B) around the wire. ...
Les Champs Magnétiques (The Magnetic Fields) is a novel by André Breton and Philippe Soupault. ...
Magnetic Fields (also known as Les Chants Magnétiques) is the third album by Jean-Michel Jarre, and was released in 1981 on Disques Dreyfus. ...
The Magnetic Fields. ...
History of Magnetic Fields
People did not start learn very much about magnetic fields until the source t 1800's. People knew that magnetic fields existed for a long time, but the only magnetic field hey had of these fields were permanent magnets and they never had a link to electricity. For instance, when there was no electricity scientists couldn’t very well conduct experiments on it. (Spark Notes 1) It wasn’t until the early 1800's when the first connection was made between electricity and magnetism. (David Stern 1) Before the 1820's people believed that the inside of the earth was magnetized like lodestones. This may have been because lodestone and iron were the only magnets known before the 1820's.(Spark Notes 2) Lodestones are natural magnets of iron-rich ore. By the mid 1900's scientists knew that electric currents flowed in space. They learned this after observing how solar eruptions led to magnetic storm disturbances. They were still trying to figure out where the currents flowed and why the solar wind existed (Wikipedia 3). It took many years and experiments to discover and many scientists are still experimenting on magnetic fields today. Early experiments grew to the knowledge we have on magnetic fields today.(Stern 1) Scientists were confused when they discovered that the direction of the compass needle at any place shifted slowly, suggesting a slow variation of the earths magnetic field. This discovery was made right after the theory of magnetic fields was made so people knew nothing about magnetic fields at this point. For example the theory wasn’t supported very well so nobody really had many ideas. Edmond Halley proposed that the earth contained a number of spherical shells, one inside each magnetized differently, each slowly rotating in relation to the others. There was once again no evidence of this theory but it made since to the scientists at the time. This theory was not replace for well over 600 years. The North -South pointing properly on the compass needle was discovered in China around the year 1000.This was the very first ever found proof of magnetic fields. Later in 1600's William Gilbert in London showed it could be explained if the earth was a huge magnet.(Bellis 3) He used a spherical magnet for the model of the earth, he called it “terella” which means little earth. Gilbert moved a small compass over the surface of terella and demonstrated that it always pointed toward its magnetic poles. The terella experiment was the first physical model made of what somebody though magnetic fields were that actually made since at the time. It generations to discover magnetic fields. One of many experiments that ended up leading to the discovery of magnetic fields was done by Hans Christian Oersted. Oersted was a professor at Copenhagen University. His dicovery was made during a demonstration he was doing for scientists and students. He made the very first connection between electricity and magnetism in the early 1800's. Although people had already knew about magnetic fields not many people experimented on them to find out more about magnetic fields. Oersted conducted his experiments using compasses and needles. He conducted his experiment like this because,his previous experiments consisted of two wires and he wanted to find out more information. The wire experiment resulted in being attracted to each other, but when he repeated this experiment the wires mutually repelled .( Detection of Magnetic Fields 1) This really left scientists in amazement. Because Oersted’s two experiments clearly resulted in the complete opposite of the traditional electric theory which stated “there is no interaction between the two wires”. Oersted’s experiments proved that there was a connection between electricity and magnetism. Even with the results to Oersted’s experiments scientists needed to continue experimenting on magnetic fields so they could generate a coherent definition. Scientists placed a conductor between the two wires and it had now effect on the phenomenon. Because conductors shield electric forces this phenomenon was clearly not the results of an unknown electrical interaction. After this they replaced on of the wires with a static charge, the static charge felt no forces in this experiment. Both of these experiments only lead to the conclusion that “ Magnetic fields are caused by moving charges.”Hans Christian Oersted made a major contribution to the discovery of magnetic fields. Scientists didn’t discover anything new about magnetic fields until the 1820's. Andre-Marie Ampere was a french chemist, mathematician, and philosopher who founded the science of electrodynamics.(Bellis 2) He discovered the relationship between electric currents and magnetic fields. Ampere was influenced by the findings of Oersted. For instance, Oersted made his dicovery only a few years before Ampere did. Oersted was Andre-Marie Ampere’s idol. Ampere thought that if a current exerted a magnetic force on a compass needle, then two such wires should also interact magnetically. His experiment was very similar to Oersted’s, but the few changes made a great impact. Through a series of experiments Andre Ampere thought that the interaction was simple and fundamental. He compared his results to Oersted’s and proved his theory to be correct. For instance, putting all of the results together made it easy to see that it was a simple fundamental. He concluded that parallel currents attract and straight parallel currents are inversively proportional to the distance between them and proportional to the intensity of the current flow in each. The 1820's was a big decade for the studies of magnetic fields. Major theories and discoveries were made again in the mid to late 1800's .(Stern 3) Michael Faraday discovered the magnetic field lines and he named them “lines of force”.For instance, because magnetic fields is the force that holds planets up it only made since to call the lines of magnetic fields “lines of force”. Lines of force are imagery lines used to describe a field of force. They are closest together where the field is strongest, and farthest apart where the field is weakest. Faraday is responsible for the principals by which electric generators and transformers work, as well as for the foundations of electrochemistry. (Mifflin 6)An electrical generator is a device that produces electrical energy from a mechanical energy source using electromagnetic induction The process is known as electricity generation.(Mifflin 15) A transformer is a device used to transfer electric energy from one circuit to another, especially a pair of multiply wound, inductively coupled wire coiles that effect such a transfer with a change in voltage, current, phase, or other electric characteristic. But James Clerk Maxwell (Faraday’s younger colleague) a mathematical physicist fleshed these ideas out in mathematical terms, and “ Maxwell’s Equations” are now the cornerstone of the electromagnetic theory.(Mifflin 8)Maxwell’s equations consists of four different equations that play a role in the study of electricity and magnetism.(Bellis 1) Then in 1864 James Clerk Maxwell did an experiment unexpectedly involving the velocity of light. From this he concluded that light was an electric phenomenon, the discovery of radio waves, the theory of relativity and a great deal of present-day physics and sprang from Maxwell’s experiments. These experiments and discoveries had a great impact on the worlds knowledge of magnetic fields today. Scientists have known that the magnetic pole moves for a long time. In 1831James Ross located the pole for the first time after an arctic journey. He was there for a long time because his boat got stuck in the ice for four years! While he was there he found the arctic pole. It wasn’t found again until Roald Amundsen found it for the second time in 1904. After making some observations Amundsen realized that the magnetic pole moved at least 50 km since James Ross’ day. The magnetic pole continued to move throughout the 20th century. The poles average movement per year was 10km north, but lately it was accelerating at 40 km at this rate they will leave north America and reach Siberia in a few decades. The magnetic fields have been changing in other ways too. For instance, in Africa the compass needles are drifting about one degree per decade. And the magnetic field has weekend 10% globally since the 19th century. Although these changes may sound drastic, in the past the fields have completely switched places. These reversals are unpredictable. They change like this at irregular intervals averaging about 300,000 years the last time the poles changed like this was 780,000 years ago. Although we have known about magnetic fields for a long time we continue learning new things about them even today.( NASA 1-2)
It hasn’t been long since new information has been found on the magnetic field. In 1958 “Explorer I “discovered the earths magnetosphere while doing research for the International Geophysical Year. Explorer I was the first successful satellite for NASA. The magnetic field forms a protective bubble know as the magnetosphere. The magnetosphere shields the earth from interplanetary space weather. In August and September of 1958 “ Project Argus” was performed to test a theory about the formation of radiation belts that may have tactical use in war.field. The radiation belt is a belt of energetic electrons, protons, and heavier ions encircling the earth and trapped in the geomagnetic field. In 1959 Thomas Gold proposed the name magnetosphere when he said:
The region above the ionosphere in which the magnetic field of the earth has a dominant control over the motion of gas and fast charged particles is known to extend out to a distance of the order of ten earth radii, it may be appropriately be called magnetosphere (Wikipedia 2) The name magnetosphere was made official shortly after Thomas Gold said this. Scientists are still discovering things about the magnetic field to this day.--70.130.172.133 05:26, 5 November 2006 (UTC) This is part of a research paper |
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