The Magnetic Field and Faradays Law

The Magnetic Field and Faradays Law - The Magnetic Field...

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The Magnetic Field and Faraday’ Law Goals and Introduction The human experience with magnetism dates back many centuries, at least to the time of the ancient Greeks and Chinese, who were both aware of magnetic materials that had the ability to attract iron. It is around the year 1000 CE that the Chinese discovered that a steel needle rubbed with one of these magnetic materials would actually become magnetic as well. When allowed to move freely, they discovered that this needle would then always point in the same direction (assuming it was not near another magnetic material) – towards the magnetic north pole of the Earth. This early use of magnetism in the construction of the compass allowed for many discoveries, as humans were now able to navigate and explore the world more effectively in a systematic, efficient manner. Though the discovery of the phenomenon is centuries old, it is not until much more recent times, however, that we have understood the cause of the magnetic property of materials, and of how the space around these materials is affected by their existence. Interestingly, it was our early examinations of electric current that led to these discoveries. In the early 1800’s, it was Hans Oersted who discovered that a compass needle could deflect and point away from the magnetic north pole when near a current-carrying wire. Also, the amount of the deflection could be affected by the amount of current in the wire. This phenomenon could be explained by the idea that the current-carrying wire behaved like a magnetic material, and must affect the space around it in a similar way. Magnetic materials, and devices like the current-carrying wire, cause there to be a magnetic field in the surrounding space, such that if an object sensitive to this field is brought nearby, it may experience a force, or torque. In exploring magnetic fields created by their sources, we are thus reliant on observing or measuring electric and magnetic properties. A compass needle provides us with an excellent tool for probing and observing the direction of a magnetic field at a certain location in space. We now understand, of course, that a compass will point towards the magnetic north pole because the Earth itself generates a magnetic field. Because the needle always aligns itself in a very particular way, we designate one end of the needle as the “north” end and the other as the “south”, based on the alignment of the needle. The end of the magnetic needle that points to the north is called the “north pole” of the needle, and the end that points south is called the “south pole” of the needle. The needle is a magnet with both a north and a south pole. It can be shown however, by using two magnets whose poles we have determined, that opposite poles attract each other. The consequence of this is that what we call Earth’s magnetic north pole (because it is in the north) is actually the south pole of a huge magnetic field, and what we call Earth’s magnetic south pole (because it is in the south) is actually the north pole of a huge magnetic field!
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