APPENDIX 



A. THE ELECTRICAL APPARATUS 



FOR giving children a practical understanding of such 

 laws of electricity as affect everybody, the following simple 

 apparatus is invaluable. It is the electrical apparatus 

 referred to several times in the text. The only part of it 

 that is at all difficult to get is the Chromel resistance wire. 

 There is a monopoly on this and each licensee has to agree 

 not to sell it. It can be bought direct from the manu- 

 facturer by the school board if a statement accompanies the 

 order to the effect that it is not to be used in any com- 

 mercial devices, nor to be sold, but is for laboratory ex- 

 perimentation only. The manufacturers are Hoskins Manu- 

 facturing Company, Detroit, Michigan. 



The following diagram will make the connections and 

 parts of the electrical apparatus clear : 



FIG. 1 90. Electrical apparatus : At the right are the incoming wires. Dotted 

 lines show outlines of fuse block. A, 2 cartridge fuses, 15 A; B, 2 plug fuses, 

 10 A; C, knife switch; D, fuse gap; E, snap switch; F, H, lamp sockets; 

 G, flush switch; /, /, K, Chromel C resistance wire, No. 22 (total length of 

 loop, 6 feet), passing around porcelain posts at left. 



The flush switch (G) should be open at the bottom for 

 inspection, remove the back. The snap switch (E) should 

 have cover removed so that pupils can see exactly how it 

 works. 



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