View and Download the solved questions, solved numerical problems or 9th Class Physics notes of Chapter 9 “Transfer of Heat” of Punjab Textbook Board. These 9th class physics notes of 9th Chapter are according to the new syllabus (2013) of Punjab Boards including Lahore Board, Gujranwala Board, Sahiwal Board, Rawalpindi Board, Faisalabad Board, Multan Board, Bahawalpur Board, Federal Board, DG Khan Board and Sargodha Board. Students of 9th Class of all these board can facilitate from the physics notes given below. You can also download 9th Class Physics Chapter 9 Solved Questions and Numericals Problems.

### Unit 9: Transfer of Heat

By studying this chapter students will be able to: Recall that thermal energy is transferred from a region of higher temperature to a region of lower temperature. Describe in terms of molecules and electrons how heat transfer occurs in solids. State the factors affecting the transfer of heat through solid conductors and hence, define the term Thermal Conductivity. Solve problems based on thermal conductivity of solid conductors. Write examples of good and bad conductors of heat and describe their uses. Explain the convection currents in fluids due to difference in density. State some examples of heat transfer by convection in everyday life. Explain insulation reduces energy transfer by conduction. Describe the process of radiation from all objects. Explain that energy transfer of a body by radiation does not require a material medium and rate of energy transfer is affected by:

• Colour and texture of the surface
• Surface temperature
• Surface area