Question

5. Give reasons for the following.
(a) Freezers are placed at top of refrigerators.
(b) Tumblers used to sip hot drinks are not made of metals.
(c) The radiators of cars are painted black
(d) Handles of cooking utensils are made of wood, plastic or bakelite
(e) We feel more comfortable wearing white or light-coloured clothes in summers.
() We prefer wearing dark-coloured clothes in winters.
(g) Two thin blankets are usually warmer than one thick blanket.
(h) Gunny bags are used to prevent melting of ice.

Answer 1

Answer:

option g is correct answer

Answer 2

a)Freezers are always on top of a fridge due to the nature of convection. The natural law of convection is that warm air rises while cold air falls, so the freezer at the top provides cold air for the other compartments at the bottom of the freezer.

b) tumblers, used to sip hot drinks are not made of metals because metals absorb heat and the non metal does not absorb heat.

c)Car radiators are painted black because it emits the most heat through radiation (highest emissivity). This improves the heat transfer out of the radiator when air isn't moving through the radiator. ... Also note that many cars are intended for the area behind the grille to be black (a backdrop to the grille).

d) The handles of cooking utensils are made up of plastic or wood because plastics and wood are bad conductor of heat. As they are bad conductors of heat therefore they won't be able to pass the heat of the flame to the person's hand and will prevent the person from burns or any other injuries.

e)Because white color can reflect the sunlight. It absorbs less light, so it's comfortable to wear white clothes in the summer. On the other hand, black color absorbs sunlight greater than white color.

I)But in winters, the dark color clothes absorb a lot of heat because they are good conductors of heat, and they absorb most of the heat energy fallen on them. Thus, in summer we preferred to wear light or white color clothes and in winter, to wear dark color clothes.

G)Air is trapped in the space between two thin blankets. Since air is an insulator of heat, it prevents the escape of body heat. That is why two thin blankets are usually warmer than one thick blanket.

H)Gunny bags are made up of jute . so, the fibre of the jutes prevent heat transfer from coming inside from out side. This prevent ice to be melt. ... Hence the air in the pores of the fibre prevents any heat transfer between the ice and the surroundings.

$<b><marquee>$Hope it's helpful...