. A text book of physics, for the use of students of science and engineering . y of the conversion of heat into mechanical work andvice versa. The first law may be enunciated as follows : Heat andmechanical work are mutually convertible, and in any operation involvingsuch conversion 4-18 x 10 ergs of mechanical work disappear for eachcalorie generated, or 4-18 x 10 ergs of mechanical work appear for eachcalorie expended. In the British system, substitute 1400 foot-lb. andone Centigrade heat unit in the latter part of the law. The student must be prepared for very large waste in all operationsi
. A text book of physics, for the use of students of science and engineering . y of the conversion of heat into mechanical work andvice versa. The first law may be enunciated as follows : Heat andmechanical work are mutually convertible, and in any operation involvingsuch conversion 4-18 x 10 ergs of mechanical work disappear for eachcalorie generated, or 4-18 x 10 ergs of mechanical work appear for eachcalorie expended. In the British system, substitute 1400 foot-lb. andone Centigrade heat unit in the latter part of the law. The student must be prepared for very large waste in all operationsinvolving the conversion of heat into mechanical work. It is verydifficult to prevent heat being dissipated into forms which are uselessfor any practical purpose. The operation of converting mechanicalwork into heat is not accompanied by such excessive waste, andlaboratory experiments on the value of Joules equivalent usuallyfollow this method. Expt. 76.—Value of Joules equivalent by Callendars machine. TheCallendar apparatus provides a very convenient laboratory method of. Fig. 363.—Calorimeter of Callendars machine. determining J, and is illustrated in Fig. 363. A brass drum A is fixed tothe end of a shaft and can be rotated by means of a band passed over apulley B ; the band is driven by a small electromotor not shown in A revolution counter at D enables the number of revolutions of thedrum to be observed. The drum serves the purpose of a calorimeter, andcontains a measured quantity of water ; a bent thermometer C passesthrough a central hole in the end of the drum and dips into the water. Aband brake, made of three strips of silk ribbon, passes round the drum andcovers nearly the whole of its external cylindrical surface. The brake 356 HEAT CHAI\ carries a dead load W at one end (Fig. 364), and has a shackle E attachedto the other end to which smaller weights w may be added. A light spring balance pulls the shackle E upwards andenables the brake load to be read
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
