TOPIC 9 Transfer of Thermal Energy 9.1 Conduction and Convection Q1. A rod of metal is heated at one end. Which statement best describes the conduction of heat through the metal? A Atoms move from the hot end and hit electrons at the cold end. B Atoms vibrate and hit atoms at the cold end. C Free electrons move from the hot end and hit atoms further along the rod. D Free electrons vibrate and pass energy to free electrons further along the rod. [June 2012/P11/Q17] Q2. How is heat conducted in a metal? CW S.S sionT A by movement of electrons through the metal only B by movement of atoms through the metal only C by vibration of atoms and movement of electrons through the metal D by vibration of atoms only [June 2012/P12/Q17] Q3. Four metal cans are identical except for the colour and the texture of their outer surfaces. 100 cm3 of water at 70 ? is poured into each can. Which cools the most rapidly? A B C D igol outer surface: black, rough black, shiny white, rough white, shiny [Nov 2012/P12/Q17] Q4. Two identical metal plates are painted, one matt (dull) white and the other matt black. These are placed at equal distances from a radiant heater as shown. The heater is turned on for five minutes. matt white metal plate radiant heater matt black metal plate
Topic 9 Transfer of Thermal Energy @ Page 2 OL Physics P1 Which metal plate absorbs more energy and which plate emits more energy in this time? absorbs more A black B black C white D white emits more black white black white [June 2013/P12/Q16] Repeat [June 2013/P11/Q14] Q5. A glass beaker contains water. When the centre of the base of the beaker is heated, a convection current is set up. glass beaker -> -1-> ---. convection current water Which statement explains this? heat A The evaporation of water causes water molecules to rise to the surface. B The expansion of water molecules causes them to rise to the surface. C The water above the heat source rises because it becomes less dense. D The water at the sides sinks because it becomes less dense. [June 2013/P11/Q13] Q6. On a cold afternoon, a house loses 54 MJ of thermal energy (heat) to its surroundings as shown. thermal energy lost through roof thermal energy lost through windows thermal energy lost through walls thermal energy lost through floor The heating system must supply more than 54 MJ of thermal energy to keep the temperature of the house constant. Which statement explains this? A The extra thermal energy is lost from the house to the surroundings by other means. B The extra thermal energy keeps the house warmer than the surroundings. C The temperature of the surroundings decreases continuously during this period. D The thermal insulation of the roof is extremely ineffective. [Nov 2013/P11/Q13]
Topic 9 Transfer of Thermal Energy 5 Page 3 OL Physics P1 Q7. A saucepan is used