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Answer:
Convection is a type of radiation that is made up of heat natural ventilation is how air circulates. People prefer to wear dull cloths in the winter because darker colors absorb more light and they wear white clothing in the summer because white reflects light. Hope this helps
Explanation:
Answer:
8 Heat convection is a mode of heat transfer by the mass motion of a fluid such as air. Heat convection occurs to the surface of an object where the surrounding fluid of object is heated and moved energy away from the source of heat.
9 In case of solids, the molecules can just vibrate around their mean position, but cannot move from one place to another place. As the particles cannot travel to source of heat, therefore convection in solids is not possible.
10 Natural ventilation is a method of supplying fresh air to a building or room by means of passive forces, typically by wind speed or differences in pressure internally and externally.
11(a) Black and dull clothes are good absobers and radiators of haeat while white and shining clothes are poor absobers and radiators of heat . Because of this reason people prefer to wear dull and black clothes in winter.
(b) We prefer white clothes in summer because white clothes reflect most of the sun's heat and absorb very little of the sun's heat and keeps our body cool. We prefer to wear black or dark coloured clothes in winter as dark clothes absorb most of the sun's heat and keep our body warm.
12 When you sit by a campfire, most of the heat you are receiving from the fire does not come from hot air. It comes from thermal radiation.
13 A beaker whose surface is painted black will cool first as black bodies radiate heat faster. It will radiate heat at a higher rate than the other beaker that is covered and will cool quickly. Hence (b) is the correct option.
14 In conduction, heat transfer takes place between objects by direct contact. In convection, the heat transfer takes within the fluid. In radiation, heat transfer occurs through electromagnetic waves without involving particles. The heat transfer takes place due to the difference in temperature.
15 In the case of the Celsius scale, the lower point is the melting point of pure ice at normal atmospheric pressure and the upper fixed point is the boiling point of pure water at normal atmospheric pressure (1atm). ... This is the boiling point of pure water at normal atmospheric pressure (1atm or 1.01325×105Pa).
16 And just like the coats people wear, birds tend to get puffier in winter. “A bird's body heat warms the air between its feathers,” Marra explains. “So birds fluff up in the cold to trap as much air in their feathers as possible.
17 We wear dark coloured clothes in winter to keep us warm as they absorb all the heat radiation coming from the sun whereas light coloured clothes reflect most of the heat radiation that falls on them and therefore we feel more comfortable wearing them in the summer.
18 (a) A clinical thermometer reads temperature 35°C to 45°C while the range of laboratory thermometer is -10°C to 110°C.
(b) The clinical thermometer has a kink near the bulb while there is no kink in the laboratory thermometer.
19 (a) Examples of insulators include plastics, Styrofoam, paper, rubber, glass and dry air. The division of materials into the categories of conductors and insulators is a somewhat artificial division.
(b) Examples of conductors include metals, aqueous solutions of salts (i.e., ionic compounds dissolved in water), graphite, and the human body. Examples of insulators include plastics, Styrofoam, paper, rubber, glass and dry air.
Explanation:
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