18 ELEMENTS OF LABORATORY WORK 



Additional Exercises and Questions. 



1. Calculate the number of cubic millimetres in a cubic inch. 



2. If 2 litres of air weigh 2-5854 grams, what is the density of air ? 



3. If the pitch of a screw is 1 millimetre and its circular head is 

 divided into 100 equal divisions, calculate the linear distance corre- 

 sponding with a turn of the circle through 73 divisions. 



4. Determine the pitch of a screw by direct comparison with a scale, 

 and also by ascertaining its linear movement when turned within a fitted 

 hollow screw. 



5. Measure the circumference of a penny by marking it and rolling 

 it along a scale. Then measure its diameter and calculate from it the 

 circumference. 



6. Read the height of the barometer by using the vernier. 



7. Take several readings of angles by using the vernier on a spectro- 

 scope. 



8. Ascertain the diameter of a wire by using the screw-gauge. 



9. Find the thickness of a microscopic cover-glass by using the 

 spherometer. Also measure several cover-glasses and compare the re- 

 sult with the last observation. 



10. How may microscopes be utilised for measuring very small 

 distances ? 



11. How is a long distance best measured ? What difficulties have 

 to be overcome and what precautions are needed ? 



12. Suggest methods for measuring irregular areas. 



13. Compare the densities of several liquids by weighing the same 

 body in each. 



14. Observe the alteration of density, when the temperature of 

 water is raised, by showing that the counterpoise obtained when a 

 body is weighed in cold water is not maintained if warm water is sub- 

 stituted for the cold. 



15. Suggest a method of determining the density of a body lighter 

 than water. Test your method. 



16. How could the density of a gas be found out ? 



1 7. What precautions are necessary in determinations of density, 

 and what conditions have to be attended to ? Give the observations, in 

 order, which are needed in an exact determination of density in the 

 case of () a gas, (&) a liquid, and (c) a solid. 



