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