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