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