1. Difference between atoms and particles (e.g. conduction --> atoms of the hot end vibrate and hit the neighbouring atoms to transfer heat... then can I replace atoms by particles in the above sentence?)
2. Why larger temperature difference between two ends and larger cross-sectional area of conductor can affect the rate of conduction? And are they increasing or decreasing the rate of conduction?
3. Are good conductor of heat equal to good conductor of electricity? Or any exceptions?
4. Can you give some examples of convergent light beam? Any why?
Thanks a lot :D
F3 Physics
2011-04-10 11:31 pm
回答 (1)
2011-04-12 5:25 am
✔ 最佳答案
1. Heat transfer by conduction is carried out mainly by free electrons, not atoms. Here, the particles actually refer to free electrons.2, A higher temperature at one end causes free electrons to vibrate more vigorously. The vigorous vibrations could transmit much faster than less vigorous vibrations. This is similar to a higher pressure difference at two ends of a pipe causes wtaer to flow through the pipes more quickly.
Larger cross-sectional area means more number of electrons are excited. This helps to transmit more heat. Again, this siutation is similar to a pipe with larger cross-sectional are allows more water to flow through it.
Raising the temperature difference between the two ends of a conductor or increasing its cross-sectional area would increase the amount of heat flow.
3. Yes. Free electrons are responsible for both heat conduction and electrical conduction. Because metals have plenty of free eelctrons, hence they are good heat conductors and electrical conductors.
4. In a CD reader, the laser beam is focussed by a convex lens to produce a very fine beam for reading of the digital signals recorded on the CD. This is an example of a convergent light beam.
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