. A-B-C of electricity. ir, and it is owing to this close re- 16 MAGNETISM lation that we are able to obtain so manywonderful things by the use of electricity. We shall now show you how electricityproduces magnetism, and, when we come tothe subject of electric lighting we will explainhow magnetism produces electricity. The easiest way to show how electricitymakes magnetism is to find out how magnetsare made. Supposewe wanted to make ahorseshoe magnet, justmentioned above; wewould take a piece ofsteel and wind aroundit some fine copperwire, commencing onone leg of the horse-shoe and windingarou
. A-B-C of electricity. ir, and it is owing to this close re- 16 MAGNETISM lation that we are able to obtain so manywonderful things by the use of electricity. We shall now show you how electricityproduces magnetism, and, when we come tothe subject of electric lighting we will explainhow magnetism produces electricity. The easiest way to show how electricitymakes magnetism is to find out how magnetsare made. Supposewe wanted to make ahorseshoe magnet, justmentioned above; wewould take a piece ofsteel and wind aroundit some fine copperwire, commencing onone leg of the horse-shoe and windingaround until we cameto the end of the otherleg. Then we should have two ends of wireleft, as shown in the sketch. (Fig. 3.) We connect these two ends with an electricbattery, giving, say, two volts, and then theamperes of current of electricity will travelthrough the wire, and in doing so has suchan influence on the steel that it is convertedinto a magnet, such as you have playedwith. The current is broken—that is to 2 17. Fig. 3 A-B-C OF ELECTRICITY say, it is shut off several times in making amagnet of this kind, and then the wire is takenaway from the battery and is unwound fromthe steel horseshoe, leaving it free from wire,just as you have seen it. This horseshoe isnow a permanent magnet—that is, it willalways attract and hold pieces of iron andsteel. Now, if you were to do the same thingwith a horseshoe made of soft iron instead ofsteel it would not be a magnet after youstopped the current of electricity from goingthrough the wires, although the piece of ironwould be a stronger magnet while the elec-tricity was going through the wire around it. The steel magnet is called a permanentmagnet, and its ends, or poles, are namedNorth and South. There is usually a loosepiece of steel or iron, called an armature,put across the ends, which has the peculiarproperty of keeping the magnetism from be-coming weaker, and thereby retaining thestrength of the magnet. The strongest partof t
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectelectri, bookyear1915
