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How to Make a Galvanometer - Easy Science Projects A galvanometer is an instrument used to detect the presence of an electrical current in a circuit or to measure the value of the current in amperes. The operation of practically all galvanometers is based upon the same principle, and they differ chiefly in mechanical construction and the relative arrangement of their different parts. A very simple galvanometer, that will give quite satisfactory results, under favorable conditions, may be constructed as follows: Turn from a piece of hard wood a ring having dimensions corresponding to those given in the cross section, Fig. 1. Fill the groove in this ring to within 1/8 in. of the top with No. 18 gauge double-cotton-covered copper wire, insulating the different layers from each other by means of a layer of good bond paper. The winding may be started by drilling a small hole through the side of the groove, as close to the bottom as possible, and allowing about 6 in. of the wire to protr...

How to Make a Rheostat In operating small motors there is as a rule no means provided for regulating their speed, and this often is quite a disadvantage, especially in the case of toy motors such as used on miniature electric locomotives. The speed, of course, can be regulated by changing the number of cells of battery by means of a special switch, but then all the cells are not used the same amount and some of them may be completely exhausted before the others show any appreciable depreciation. If a small transformer is used with a number of taps taken off the secondary winding, the voltage impressed upon the motor, and consequently the speed, can be changed by varying the amount of the secondary winding across which the motor is connected.   Diagram Showing the Connections for a Small Motor Where a Rheostat Is in the Line (Fig. 1) But in both these cases there is no means of varying the speed gradually. This can, however, be accomplished by means of a small rheostat placed...

How to Make an Anemometer for a Science Project - An Electric Anemometer By Wm. H. Dettman The construction of this instrument is so simple that any amateur can make one and if accurate calibrations are desired, these can be marked by comparison with a standard anemometer, while both are placed in the wind. The Indicator The case of the indicator is built of thin wood—the material of an old cigar box will do—9 in. long, 6 in. wide and 1-1/2 in. deep. If cigar-box material is used, it must first be soaked in warm water to remove the paper. If a cover is to be used on the box, a slot, on an arc of a circle, must be cut through it to show the scale beneath. The arc is determined by the length of the needle from a center over the axis on which the needle swings. When the box is completed, smooth up the outside surface with fine sandpaper and give it a coat of stain. The core of the magnet is made by winding several layers of bond paper around a pencil of sufficient size to make an in...

How to Keep Birds Away From Garden -  A Garden-Bed Scarecrow A very neat and successful scarecrow for garden beds can be made as follows: A number of corks are procured, and a feather is stuck in each end of them, as shown. These are tied to a string, spacing them from 1 to 2 ft. apart, and the string is hung over the beds. The slightest breeze will keep them fluttering, and no bird will come to rest on the beds. The Fluttering Feathers Attached to the String with Corks Scare the Birds Away —Contributed by M. T. Canary, Chicago. Excerpt from the book: THE BOY MECHANIC - BOOK 2 1000 THINGS FOR BOYS TO DO HOW TO CONSTRUCT DEVICES FOR WINTER SPORTS, MOTION-PICTURE CAMERA, INDOOR GAMES, REED FURNITURE, ELECTRICAL NOVELTIES, BOATS, FISHING RODS, CAMPS AND CAMP APPLIANCES, KITES AND GLIDERS, PUSHMOBILES, ROLLER COASTER, FERRIS WHEEL AND HUNDREDS OF OTHER THINGS WHICH DELIGHT EVERY BOY WITH 995 ILLUSTRATIONS PUBLISHED 1915, BY H. H. WINDSOR CHICAGO POPULAR MECHANICS CO. PUBL...