Intermediate physics / by W. Watson.

  • Watson, W. (William), 1868-1919.
Date:
1912
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Licence: In copyright

Credit: Intermediate physics / by W. Watson. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    9. Describe Bunsen's ice calorimeter, and explain how you would use the instru- ment to determine the specific heat of a solid. If 1 gram of water expands by '0918 c.c. on freezing, and evolves 80 calories, calculate the specific lieat of a substance, 5 grams of which when introduced into a Bunsen's ice calorimeter at a temperature of 100° C. produces a con- traction of 700 cubic mm. 10. Describe some method by which the specific heat of a gas at constant pressure can be determined. 11. How can the vapour pressure of water be determined at temperatures higher than 100°. If you were given a curve showing the vapour pressure of water, explain how the pressure-gauge of a steam-boiler might be replaced by a thermometer. 12. Explain what is meant by the steam line, the hoar-frost line, and the ice line, and what is indicated at the point where they meet. 13. Why do two thermometers, one with its bulb dry and the other with its bulb moist, generally indicate diff'erent temperatures when exposed to the air at the same place ? Under what conditions would the readings of the two thermometers be identical ? 14. Explain how the humidity of the air can be obtained by determining the dew- point. What data would you require and what assumptions would you make in obtaining your result ? 15. If some of the air of the room is introduced into a bottle which is then corked, what change, if any, would take place (1) in the dew-point and (2) in the relative humidity of the contained air if the temperature of the bottle is raised ? 16. Ice, water, and salt are mixed, two and two, in approximately equal proportions, each being originally at 0° C. Which of the three mixtures will be at the highest and which at the lowest temperature ? Give reasons for your answer. 17. Explain what is meant by a eutectic, and show that the composition of the eutectic of, say, copper-silver can be deduced from the cooling curves for a number of alloys. 18. Explain what is meant by the calorific power of a fuel. Given that 1 gram of carbon when burnt to carbon dioxide liberates 7860 calories, and when burnt to carbon monoxide it liberates 2140 calories, what proportion of the energy of a carbonaceous fuel is wasted if the flue gases contain equal volumes of COg and CO. CHAPTER IV 1. Explain carefully how heat is conveyed through a liquid by convection, and describe some practical application of tliis phenomenon. 2. How do you explain the fact that if a piece of metal gauze is held above a gas- burner, and the gas is lighted above the gauze, the flame does not go below the gauze ? 3. Describe and explain the action of the miner's safety-lamp. When does the lamp become dangerous ? 4. Give a careful definition of thermal conductivity. Estimate the rate at which ice will melt in a wooden box 2 cm. thick, of inside measurements 100 x 60 x 60 cm., assuming that the conductivity of wood is 0'00040 and that the external temperature is 20° C. 5. How much heat will be transmitted through each square metre of an iron boiler plate, 4 mm. thick, in an hour if the opposite faces are kept at 300° and 120° respectively ? The conductivity of iron is 0 '2. 6. The outside of a glass beaker is kept at 100° C, and it contains a mixture of ice and water which is kept well stirred. If the thickness of the glass is half a millimetre and the area is 200 sq. cm., find the amount of ice melted per minute if the conductivity of glass is '002 in C.G.S. centigrade units. 7. A boiler is made of iron, 06 cm. thick and of conductivity 0*2. A crust 06 cm. thick is formed inside of conductivity 0*01. If the outside of the iron is at 300°, and the inside of the crust is at 150°, what quantity of heat is conducted through each square centimetre per second ?