Question

the bulb of thermometer A is coated with lampblack and bulb of thermometer B is <br /><br />covered with silver. Both the thermometers are placed in sunshine for equal time.<br /><br />a) Which thermometer shows a higher rise in temperature?<br /><br />b) What conclusion you have drawn from the above observation?

Answer 1

We know that black bodies are good heat absorber and radiator. While white bodies like silver(Ag) is not so good absorber of heat.
Hence, The thermometer "A" which was coated with lamp-black show higher rise in temperature by its Mercury.

Answer 2

Solution : When the bulb of thermometer A is coated with lampblack and bulb of thermometer B is covered with silver and  both the thermometers are placed in sunshine for equal time then thermometer A will shows a higher rise in temperature.

• When two thermometer one is coated with with lamp black and other other is coated with silver are exposed in sunlight , the thermal radiations will absorb heat
• Black color is a good absorbent of heat , and white color is good radiator of heat
• Here since black is a good absorbent of heat so the black color in thermometer A will absorb more temperature.
• Silver is poor absorbent of heat so it will absorb liss temperature.
• That's why temperature in thermometer A will be more than temperature in thermometer B
• But eventually both will attain same temperature because as time increases the temperature in thermometer B will be equal; to temperature in thermometer .

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