# University of New Zealand. — Physical Science. — Paper a. Heat, including Radiant Heat

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## Papera. Heat, including Radiant Heat.

 1 Describe the process of measuring the specific heat of a small piece of metal. "What circumstances must be taken into account and allowed for if the result is to be relied on as accurate? 2 Tabulate briefly the various methods which have been proposed for determining the value of Joule's mechanical equivalent of heat; and describe in particular one depending upon the measurement of the heat evolved in a voltaic circuit. 3 Carnot found the efficiency of a perfect heat-engine to depend not only on the difference of temperature between the heater and the refrigerator, but also upon the temperature of the heater as measured from a certain point below the ordinary zero. Show that in an engine in which air is the working substance, that point will be at 273 degrees (Centigrade) below the freezing-point. 4 What is Newton's law of cooling? State it mathematically, and describe an experimental method of verifying it. Why is it not true for wide ranges of temperature?page 2 5 Describe the phenomena which are observed when a liquefied gas is slowly allowed to expand, (a) at a temperature much lower than its critical point, (b) at a temperature just below its critical point, (c) at a temperature just above its critical point. Can a solid body have a critical point? 6 Give a brief outline of the kinetic theory of gases, and explain in particular how it is that gases exert a pressure upon the surface of a solid body, and why that pressure is greater if the solid be warm than if it is cold. 7 Give some account of the researches of Melloni on the opacity of bodies to radiant heat. Explain also one of the methods by which the heat-rays of the spectrum have recently been investigated. 8 Explain the formation of dew? How is the relative humidity of the atmosphere measured? In what way does the degree of saturation of air with aqueous vapour depend upon the temperature?