E.—la.

B.—Heat.

1. State exactly how you would determine and mark the position of the upper fixed point (boiling-point) upon the stem of an ungraduated quicksilver thermometer. 2°What would you do to ascertain approximately the coefficient of linear expansion of a given rod of metal ? 3. Give a careful explanation of some method of compensating the expansion of the pendulum or the balance-wheel of a clock. Why is this compensation desirable ? 4. In what way does the thermal expansion of water differ from that of most other liquids ? In what way does this peculiarity affect the freezing of large bodies of water? 5. How would you verify the statement that copper is a better conductor of heat than zinc ? 6. Describe experiments which show that surfaces which absorb heat readily emit it with facility, while those surfaces which absorb little emit little. 7. Define the term " specific heat," and explain how the specific heat of a substance may be measured by means of an ice calorimeter. 8. Write a careful statement of the way in which you would determine the melting-point of a given sample of paraffin.

Sound, Light, and Heat. — For Civil Service Senior. Time allowed : Three hours. [A candidate may not answer questions from both sections of the paper. All answers should be illustrated. where possible, by diagrams.] A. Sound and Light. 1. Describe the motion of the end of a prong of a vibrating tuning-fork. How may this motion be accurately represented graphically ? 2. Explain the relation between the velocity of sound in air and the temperature of the air. What explanation has been given of the fact that sound is often audible at a greater distance at night than in the daytime ? 3. Why is the pitch of a note modified by translation of the source of sound towards or away from the observer, as in the case of the whistle of a railway locomotive passing a person standing by the line ? 4. Tuning-forks are often mounted on wooden boxes open at one end. What is the object of this, and what dimensions would you propose to give to the box in the case of a tuning-fork making 256 vibrations a second ? 5. How is the luminosity of a source of light ordinarily measured ? Give some description of the apparatus usually employed in practice. Show that, if two sources of light directly and equally illuminate a given surface, their luminosities are proportional to the squares of their distances from that surface. 6. At what distance from a concave spherical mirror of given focal length must an object be placed that the image may be half the size of the object ? 7. Explain exactly how you would measure the focal length of a plano-concave lens. 8. Make a careful sketch of the arrangement of lantern, slit, lens, and prism required to throw a well-defined spectrum upon a screen. Show in your sketch the course of a pencil of the rays. B. Heat. 9. What do you understand to be the difference between hot water and cold water? 10. Explain exactly what you would do in order to determine the freezing-point on a recently made and not yet divided mercurial thermometer. How would you expect the position of the point to vary with the lapse of time ? 11. What is meant by the apparent expansion of a liquid ? Show that the apparent expansion is approximately equal to the real expansion less the expansion of the containing vessel. 12. A litre of dry air at O°C. and 76 cm. pressure weighs 1-293 grams. At what temperature will a litre of dry air weigh exactly one gram when the pressure is 70 cm. ? 13. Describe accurately the process you would adopt in order to determine the specific heat of tin by the method of mixtures. State the nature of the calorimeter, of the thermometer, and of the other appliances you would require. 14. Twenty grams of powdered ice are shaken up with a kilogram of turpentine, the temperature of which is 80° C. Find the final temperature of the mass, assuming that the latent heat of fusion of ice is 80 and the specific heat of turpentine 0-437. 15. A common experiment on thermal conductivity is to join two similar bars of different metals end to end, to attach small equal weights with wax to the further ends of the bars, and then to heat the junction of the bars by means of a flame. The wax melts at the end of one bar sooner than at the end of the other. Show clearly why such an experiment fails to afford any definite information as to the relative conductivities of the two metals. 16. Give some account of experiments which show that for a given kind of radiation the absorbing power of a surface is proportional to its radiating power.

Magnetism and Electricity. — For Civil Service Junior. Time allowed: Three hours. 1. How would you ascertain whether a wire nail which had been magnetised retained any residual magnetism? 2. What is meant by a " line of force "? Make a sketch of the lines of force in the field due to (a) a bar magnet, (b) a horseshoe magnet, (c) a bar magnet with a piece of soft iron near one of its poles. 3. What do you understand by the term " magnetic meridian"? If you were asked to mark on a table the position or direction of the magnetic meridian, what would you do ?

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