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