Class 9 Physics Notes Chapter 9

Complete Notes of Class 9 Physics Notes Chapter 9 Transfer of Heat of 9th Class Physics English Medium written by Professor Tayyab Shahzad. These computerized notes are very helpful in the preparation of Transfer of Heat for students of the Class 9 Physics Notes Chapter 9 these are according to the paper patterns of all Punjab boards.

• Here are the detailed 9th class physics chapter 9 notes to help you prepare for your exams.
• Transfer of Heat Exercise Multiple Choice Questions ( MCQs ) with correct Answers
• Transfer of Heat Exercise Short Questions with Answers
• Why metals are good conductors of heat?
• Explain why. (a) A metal feels colder to the touch than wood kept in a cold place! (b) The land breeze blows from the land towards the sea! (c) The double-walled glass vessel is used in the thermos flask! (d) Deserts soon get hot during the day and soon get cold after sunset!?
• Why transfer of heat in fluids take place by convection?
• Why conduction of heat does not take place in gases?
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• What measures do you suggest to conserve energy in houses?
• What is meant by convection current?
• How does heat reach us from the sun?
• Suggest a simple activity to show the convection of heat in gases not given in the book.
• How various surfaces can be compared by a Leslie cube?
• Explain the impact of the greenhouse effect on global warming.
• What is the greenhouse effect?  
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• TEMPERATURE DIFFERENCE BETWEEN ENDS: Thus, thermal conductivity of a substance can be defined as:
• "The rate of flow of heat across the opposite faces of a metre cube of a substance maintained at a temperature difference of one kelvin is called the thermal conductivity of that substance".
• Use of conductors and non conductors class 9: In houses, good thermal insulation means lower consumption of fuel. For this, following measures may be taken to save energy.
• Hot water tanks are insulated by plastic or foam lagging.
• Wall cavities are filled with plastic foam or wool.
• Ceiling of rooms is covered by insulating materials (false ceiling).
• Important notes of computer physics ch 9 class 9 notes for Matriculation part-I students.
• Why a balloon inflated with hot air? A liquid or a gas becomes lighter (less dense) as it expands on heating. Hot liquid or gas rises up above the heated area. The cooler liquid or gas from the surroundings fills the place which in turns is heated up. In this way, all the fluid is heated up. Therefore, transfer of heat through fluids takes place by the actual movement of heated molecules from hot to cold parts of the fluid.
• "Transfer of heat by actual movement of molecules from hot place to a cold place is known as convection".
• Convection currents in air class 9: Gases also expand on heating, thus convection currents are easily set up due to the differences in the densities of air at various parts in the atmosphere.
• USE OF CONVECTION CURRENTS: Convection currents set up by electric, gas or coal heaters help to warm our homes and offices. Central heating systems in buildings work on the same principle by convection. Convection currents occur on a large scale in nature. The day-to-day temperature changes in the atmosphere result from the circulation of warm or cold air that travels across the region. Land and sea breezes are also the examples of convection currents.
• LAND AND SEA BREEZES: Why does sea breeze blow during the day?
• Land and sea breezes are the result of convection. On a hot day, the temperature of the land increases more quickly than the sea. It is because the specific heat of land is much smaller as compared to water. The air above land gets hot and rises up. Cold air from the sea begins to move towards the land as illustrated. It is called sea breeze. Why does land breeze blow in the night? At night, the land cools faster than the sea. Therefore, air above the sea is warmer, rises up and the cold air from the land begins to move towards the sea as illustrated. It is called land breeze. Land breeze blows ea during night.