19_galv_motors - Lesson 19: Galvanometers & Electric Motors...

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Galvanometers and electric motors are both based on the same basic principle of an external magnetic field exerting a force on a current carrying wire. The difference is in how far the device is allowed to move. Galvanometers are typically used inside meters (e.g. voltmeters), so the device is only supposed to move a little bit, usually against a restraining spring. Motors must be able to move freely and rotate through complete 360 o turns. Galvanometers Without getting in to all the details of the connections to a meter, the basic parts of a galvanometer are a coil of wire in a magnetic field. Although this coil of wire will usually go around and around a bunch of times in a real galvanometer, my diagrams will only show a single loop for simplicity. The external magnetic field could be made by two separate magnets, a horseshoe magnet, or an electromagnet; it doesn't really matter. The electron flow current is flowing into and out of the loop as shown by the arrows. Each section of the wire is labeled by letter so we can keep track of what is happening in each section of wire. Section “a” This is the first section of wire truly in the magnetic field. Since it is parallel to the magnetic field ( North to South ), there will be no magnetic force exerted on this section. Section “b”
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This note was uploaded on 12/02/2011 for the course PHYSICS 235 taught by Professor Staff during the Fall '08 term at Rutgers.

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19_galv_motors - Lesson 19: Galvanometers & Electric Motors...

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