Ncert- science – class 7- Chapter 3 – Heat 1 Welcome to your Ncert- science - class 7- Chapter 3 – Heat 1 1. Thermal insulation is used to stop the flow of heat absorb heat reduce the flow of heat reverse the heat flow direction None 2. The velocity of heat radiation in vacuum is Greater than that of light Equal to that of sound Less than that of light Equal to that of light None 3. Mark correct option or options : Sun temperature is measured by radiation pyrometer Both Sun temperature is measured by radiation pyrometer and Insect temperature is measured by thermocouple thermometer Moon's temperature is measured by thermometer Insect temperature is measured by thermocouple thermometer None 4. The standard fixed point for temperature measurement is used these days is : none of the above that temperature at which ice, water and water vapour coexist melting point of ice at S.T.P. that temperature at which pure ice and pure water coexist None 5. Which of these we could identify as cold with our sense of touch? Hot tea A glass of water Cup of hot coffee Ice None 6. Two thermometers are constructed in such a way that one has a spherical bulb and the other has elongated cylindrical bulb. The bulbs are made of same material and thickness. Then : both bulbs will respond same to temperature changes none of both bulbs respond to temperature changes spherical bulb will respond more quickly to temperature changes cylindrical bulb will respond more quickly to temperature changes. None 7. Mercury is often used in clinical thermometers. Which one of the following properties of mercury is not a reason for this ? It is shiny It is a liquid at room temperature It has high density. The coefficient of the thermal expansion is large None 8. Weather reports are made using __________ thermometer None of these Maximum-minimum Laboratary Clinical None 9. A metal spoon is placed in one of two identical cups of hot coffee. Why does the cup with the spoon have a lower temperature after a few minutes ? None of these Energy is removed from the coffee mostly by radiation through the spoon. Energy is removed from the coffee mostly' by convection through the spoon. Energy is removed from the coffee mostly by conduction through the spoon. None 10. Choose the correct alternative:In the process of convection, heat travels sideways in all direction downwards upwards None 11. The layers of the atmosphere are heated through (b) and (c) both Radiation Conduction Convection None 12. If the temperature of a hot body is increased by 50% then the increase in the quantity of emitted heat radiation will be 300% 125% 400% 200% None 13. Woollen clothes are used in winter season because woollen clothes Provide heat to body continuously Are bad conductors of heat Absorb heat from surroundings Are good sources for producing heat None 14. Snow is more heat-insulating than ice, because Density of ice is more Ice is more bad conductor than snow Air is filled in porous of ice Air is filled in porous of snow None 15. Glass cracks when heated; while a metal does not because Glass is bright Glass is a bad-conductor None of these Glass has pores inside None 16. Two thermometers are used to record the temperature of a room and the bulb of one is wrapped in a wet hanky. The temperature recorded by both will be same The temperature recorded by the wet-bulb thermometer will be greater than that recorded by the other None of the above The temperature recorded by dry-bulb thermometer will be greater than that recorded by the other None 17. Why is sense of touch not reliable? None of these It might misguide us It doesn't tell us what is hot or cold It doesn't work for all of us None 18. In which of the following process convection does not take place primarily? Warming of glass of bulb due to filament Boiling of water Sea and land breeze Trade wind None 19. A thermos flask is polished well To reflect all radiations from outside For shining To absorb all radiations from outside To make attractive None 20. A beggar wrapped himself with a few layers of newspaper on a cold winter night. This helped him to keep himself warm because Air trapped between the layers of newspaper is a bad conductor of heat. Friction between the layers of newspaper produces heat. Newspaper is a conductor of heat. Newspaper is at a higher temperature than the temperature of the surrounding. 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.
