APPENDIX. 347 



THERM = small calory = quantity of heat required to warm one gram of water at its 



temperature of maximum density one degree Centigrade. 



THERMAL UNIT, BRITISH = the quantity of heat required to warm one pound of water 

 at its temperature of maximum density one degree Fahrenheit = 252 gram-calories. 

 VOLT. The unit of electromotive force (E. M. F.). The international volt is "the elec- 

 tromotive force that, steadily applied to a conductor whose resistance is one inter- 

 national ohm, will produce a current of one international ampere, and which is rep- 

 resented sufficiently well for practical use by 1000/1434 of the electromotive force 

 between the poles or electrodes of the voltaic cell known as Clark's cell, at a temperature 

 of 15 C and prepared in the manner described in the accompanying specification." 

 = io 8 E. M. U. = 1/300 E. S. U. See pages xxxiv and 261. 

 VOLT-AMPERE. Equivalent to Watt/ Power factor. 



WATT. The unit of electrical power = io 7 units of power in the C. G. S. system. It is re- 

 presented sufficiently well for practical use by the work done at the rate of one Joule 

 per second. 



Watts = volts X amperes = amperes 2 X ohms = volts 2 / ohms (direct current or alter- 

 nating current with no phase difference). 

 For conversion factors see page 237. 

 Watts X seconds = Joules. 



WEBER. A name formerly given to the coulomb. 

 YEAR. See page 109. 



Anomalistic year = 365 days, 6 hours, 13 minutes, 48 seconds. 

 Sidereal " = 365 " 6 " 9 " 9.314 seconds. 

 Ordinary " = 365 " 5 " 48 46 + 



Tropical " same as the ordinary year. 



