Ncert- science – class 7- Chapter 3 – Heat 2 Welcome to your Ncert- science - class 7- Chapter 3 – Heat 2 1. Lake water never completely freezes because Principle of conduction prevents it both of the above Principle of convection prevents it none of the above None 2. On a cold day when a room temperature is 15 degree C, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15 degree C, because metals have higher thermal capacity than plastics metals are good conductor of heat plastics have a higher thermal conductivity than metals plastics have a lower density than metals None 3. Identify the statement in which the mode of heat transfer is convection ? A microwave oven cooking a meal The heat from an electric stove warming a frying pan The heat of the sun warming our planet Ice cubes cooling a drink None 4. The rise in temperature of a substance depends on the quantity of heat supplied the nature of the substance the mass of the substance all the above None 5. Among the following what should not be done while or before using a clinical thermometer? Ensure that before use the mercury level is below 35 degree C Wash the thermometer with hot water. Handle the thermometer with care, as you handle any glass articles. Don't hold the thermometer by the bulb while reading it. None 6. Beaker A contains hot water. Beaker B contains cold water. Beaker C contains a mixture of hot and cold water. If initially your hand is put into a beaker containing ice, then putting your hand in which of the beakers A, B or C will give a sensation of warmth? All of the above. A C B None 7. Which of the following is not true about Laboratory thermometers ? Range of laboratory thermometer is -10C to 110C Laboratory thermometers are designed for lab purposes such as checking boiling point, freezing point etc. Laboratory thermometers are used to measure temperatures with a high degree of precision. Laboratory thermometers are used to measure body temperature. None 8. What is the use of kink near the bulb in clinical thermometer? It allows the level of the mercury to fall when taken out of the mouth It prevents the level of the mercury from rising when taken out of the mouth It prevents the level of the mercury from falling when taken out of the mouth It allows the level of the mercury to rise when taken out of the mouth None 9. In experiment of heat transfer by convection, water inside the pipe completely gets heated (with the application of heat source). This can be explained best by which of the following statements, Differences in densities produced between the bottom and the top of water , in turn produce the driving force which continuously circulates the water. both the above explains correctly all of the above A continuous conductive channel is produced between the different layers of water in the pipe which circulates the heat. None 10. Which of the following minimizes the transference of heat in a thermos flask?1. Conduction2. Convection3. Radiation 1 and 3 1,2,and 3 1 and 2 2 and 3 None 11. Choose the correct answer from the alternatives given :For measuring very high temperature, we use None of the above Thermoelectric pyrometer Platinum resistance thermometer Mercury thermometer None 12. Two thermometers are constructed in the same way except that one has a spherical bulb and the other a cylindrical bulb; which one will respond quickly to temperature changes? either Spherical bulb thermometer both equally Cylindrical bulb thermometer None 13. A laboratory thermometer is dipped in a beaker containing hot water. As the thermometer is removed the mercury level will neither rise nor fall rise fall it may rise or fall depending upon how much water is kept inside the beaker None 14. An ideal thermometer should have Large heat capacity Small heat capacity Variable heat capacity Medium heat capacity None 15. In which of the following processes, convection does not take place primarily? Boiling of water Warming of glass of bulb due to filament Heating air around a furnace Sea and land breeze None 16. Two thin blankets are warmer than one blanket of their combined thickness, this happens, because one blanket is heavier Double layer prevent transmission of heat None of the above Two blankets have large mass None 17. A long silver tea spoon is placed in a cup filled with hot tea. After some time, the exposed end (the end which is not dipped in tea) of the spoon becomes hot even without a direct contact with the tea. This phenomenon can be explained mainly by_______ conduction radiation thermal expansion reflection None 18. Suppose a liquid in a container is heated at the top rather than at the bottom. What is the main process by which the rest of the liquid becomes hot ? Sublimation Evaporation None of these Conduction None 19. A red hot brick is placed on an iron tripod stand which stands on a large block of copper. The brick loses heat by: conduction, convection, and radiation conduction and radiation conduction and convection conduction None 20. A laboratory thermometer is dipped in a beaker containing ice. As the thermometer is removed the mercury level will neither rise nor fall either rise or fall depending upon how much ice is kept inside the beaker fall rise None Time's up Please Share This Share this content Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Leave a Reply Cancel replyCommentEnter your name or username to commentEnter your email address to commentEnter your website URL (optional) Save my name, email, and website in this browser for the next time I comment.
