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