N1 Engineering Science|The Easy Way! 83
1.4 Write down an equation to represent what takes place.
2. A copper ball with amass of 3 kg and a temperature of 300 °C is dropped into water which has a temperature of 14 °C. The final temperature of the water and steel settles at 29 °C. The specific heat capacity of the copper is 390 J/kg °C and that of water 4,2 kJ/kg °C. Neglect losses and determine the amount of water that was used.
3. A steel casting is at a temperature of 450 °C. It is dumped into 20 ℓ of water at 22 °C to cool. The final temperature of the steel and water settles at 35 °C. Assume that no heat is lost and that the water has a specific heat capacity of 4,19 kJ/kg °C and the steel 490 J/kg °C. Determine; 3.1 the rise in temperature of the water, 3.2 the drop in temperature of the steel casting, and 3.3 themass of the steel casting.
Exercise 4.5 1. What happens to the volume ofmost substances when heated?
2. Describe an experiment to prove volumetric expansion. 3. Name one practical example where volumetric expansion is put to use.
4. On what principle does a bimetal strip operate? 5. What ismeant by linear expansion?
6. Describe, with the aid of neat labelled sketches, an experiment with a bimetal strip to illustrate linear expansion.
7. Give two examples where bimetal strips are used in practice.
8. Give two useful applications of linear expansion. 9. Give three examples where you have seen results of or steps to prevent the detrimental effects of thermal expansion.
10. Write down an equation to determine the change in length of a body which undergoes a change in temperature.
11. An overhead conductor has a length of 135mwhen it spans between two pylons at a temperature of 12 °C during the night. During the day the temperature of the conductor rises to 32 °C. If the temperature coefficient of the conductor is 0,017 × 10–3/°C, calculate the increase in length of the conductor.
12. During an experiment to prove linear expansion with ametal rod, the following results were obtained: initial length of the rod = 45 cm; increase in length = 1,5 mm; initial temperature = 20 °C; final temperature = 280 °C. Determine; 12.1 the final length of the rod, and
(5,033 kg or 5,033 l)
(13 °C; 415 °C; 5,357 kg)
(45,9 mm)
(451,5 mm)
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