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Continue on to Electromagnets and Motors

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Magnetic fields are very important in our world. They are everywhere. In fact did you know that the computer that you are looking into right now contains some magnetic fields? That is true because your computer most likely has a fan in it. The fan will run on a motor, and a motor is basically a device that converts electrical energy into kinetic energy. A basic motor will consist of a magnet and an electromagnet.


The way the motor works is that the electromagnet is placed in between two opposite poles of a magnet so that the north pole of the electromagnet will point to the north pole of the magnet. The south pole of the electromagnet will point to the south pole of the magnet. Naturally, the two poles will repel each other, causing the electromagnet to rotate 180º until the poles of the electromagnet attract the poles of the magnet. The electromagnet will stop in that position since the poles of the electromagnet and the magnet will attract. But motors continue to move though, so how does that happen if the motor stops after rotating 180º? This is done by doing an electromagnetic flip, in other words, you switch the poles so that they would repel and continue moving. The way the flip works is that the charges on the ends of the electromagnet switch, switching the poles also. This continually happens after every 180º turn to keep the electromagnet spinning. Attached to the electromagnet can be a fan or any device:


Motor-nail-in-horseshoe


Now we know that magnetic fields make up motors, yet there are different types of motors out there. There are small ones, large ones, strong ones and weak ones. How can we tell how strong a motor is? Well we’re going to have to know a couple things. First we need to know the magnetic field intensity (B). Then we need to know the velocity at what the wire is traveling at (v) and the length of the wire (L). That way we can get the electromotive force, or in other words, the voltage that the motor uses. So EMF = BLv. Another way of obtaining electromotive force is by knowing the magnetic flux (Ф), or the number of field lines in a certain area of a magnetic field. Magnetic flux is equal to the magnetic field intensity (B) multiplied by the area of the magnetic field (A). The negative ratio of change in magnetic flux to the change in time (t) the current is running is equal to EMF. So EMF = - ΔФ/Δt, or can be simplified as EMF = - Byv, y being the length of the magnetic field.

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