Give reasons for the following:
(a) Iron rims are heated red hot before 'fixing' them on cart wheels.
(b) A clinical thermometer has a slight bend, or kink, in its capillary tube
(c) A new quilt is warmer than an old one.
(d) A brass tumbler feels much cooler than a wooden tray on a chilly day.
(e) The bottoms of cooking utensils are often kept black
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Answers
Answer:
SURE
Explanation:
1) because metal expands on heating and contracts on cooling.
2) A clinical thermometer has a narrow kink in the capillary tube because when Mercury expands, it pushes through the kink, but when it's taken out of patient mouth, Mercury does not go back to the bulb beacuse if it. Hence, doctor can read the patients temperature easily .
3) A new quilt is warmer than an old one. ... A new quilt is warmer because the air which is trapped inside the cotton or woollen clothing acts as an insulator and does not allow the transfer of heat. However, when the quilt gets older, the air spacing of the cotton or wool gets compressed.
4)Brass is a good conductor of heat. When one touches a brass tumbler, heat is conducted from the body to the brass tumbler easily. Hence, the temperature of the body reduces to a lower value and one feels cooler. ... Thus, a brass tumbler feels colder than a wooden tray on a chilly day.
5) The bottoms of the cooking utensils are kept black because black colors absorb heat faster than any other color. For cooking, we need that the supply of heat is fast so that the food cooks quickly. This is why the bottoms of the cooking utensils are kept black in color.
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[a)Iron rims are made slightly smaller than the wheels. They are heated red hot before fixing them on the cart wheels to expand them so that they can be easily fixed on the wheels and water is poured on them to cool them. As the rims cool they contract and take the shape of the wheel and get firmly fixed on the wheels.
(b)A slight bend or kink in the capillary tube of the clinical thermometer near the bulb ensures that the mercury does not move back into the bulb when the thermometer is taken out of a person's mouth for reading.
(c)A new quilt is warmer because the air which is trapped inside the cotton or woollen clothing acts as an insulator and does not allow the transfer of heat. However, when the quilt gets older, the air spacing of the cotton or wool gets compressed it no longer remains a good insulator.
(d)Brass is a good conductor of heat. When one touches a brass tumbler, heat is conducted from the body to the brass tumbler easily. ...
Wood is a poor conductor of heat. ...
Thus, a brass tumbler feels colder than a wooden tray on a chilly day.
(e)Cooking Utensils are painted black from bottom to absorb more heat and get heated quickly. Cooking Utensils are highly polished from inside to reduce loss of heat and keep warm for a longer time.