166 



SMITHSONIAN C0NTBIBUTI0NS TO KNOWLEDGE 



VOL. 



27 



Kkami with 1st Set of Wibes. 

 First set of wires: 16 wires, 0.6 mm. diameter. 102 em. Ions; 6 wires, 0.6 mm. diameter, 42 cm. long. 



lt.-\ olution 

 turn table per 



1 1 1 L". 



L2 ii 

 13.75 

 17.25 

 20.25 

 ,0 

 22.875 

 24.56 



Veloeitj ol 

 wires, Feet 

 per minute, 



^77 



1080 



1237 



1550 



1822 



2025 



20G0 



2215 



Resistance i il 



frame and wires. 



Grammes. 



47..", 



73.5 



93.5 



144.0 



187.0 



216.0 



225.0 



250.0 



B, 



Resistance of 



wires. 

 fli-r=r>. 



13.5 



21.7 



25.5 



37.0 



45.5 



17 5 



52.0 



56.5 



Calculated resis- 

 tance of wires. 

 Grammes. 



8.88 



13.47 



17.65 



27.7 



38.4 



47.4 



49.0 



56.7 



Resistance of Frame with 2d Set of Wibes. 



Second set of wires: 15 wires, 1.2 mm. diameter, 102 cm. long; 2 wires. 1.2 mm. diameter. 42 cm. long. 



Calculated i 

 tance ol « ires. 



Grammes. 



15.35 



15.4 



22.65 



23.4 



29.9 



30.60 



49.5 



49.9 



67.4 



08.5 



S2.6 



83.2 



83.7 



Resistance of Frame with 3d Set of Wibes. 

 Third set of wires: 15 wires, 2 mm. diameter. 102 cm. long; 2 wires, 2 mm. diameter. 42 cm. long. 



Revolutions of 



turn table 

 per minute. 



9.25 

 11.55 

 L1.55 

 15.25 

 18.1 

 19.25 

 19.25 

 20.63 



Velocity <>f 



WIT'eS. I eel 



per minute. 



O'JO 



1040 

 1040 

 1375 

 1630 

 1735 

 1735 

 I860 



Resistance o1 



frame and wires. 



Grammes. R«. 



65 



91 

 101 

 160 

 203 

 221 

 216 

 237 



Resistance of 



wires. 

 B 3 — r=r,. 



37.5 



43.5 



53.5 



-,:, ii 

 86.5 

 92.0 

 87.0 

 90.5 



Calculated resis- 

 tance of wires. 

 Grammes. 



25.2 



39.35 



39.35 



68.7 



96.6 

 109.5 

 109.5 

 125.8 



The l.-isi column of these tables is calculated for a coefficient of form equal 

 to 0.5, which has been found to be approximately correct for a rigid cylindrical 



body. 



These tallies are not sufficiently extensive to determine accurately the ex- 

 act resistance that wires of various sizes will offer at given velocities, or to 

 serve as the basis for the deduction of formulae, and were not made for that 

 purpose. However, from the above data, and the curves plotted in Plate 44, 

 it will be seen that some unexpected results were obtained. 



