Standing in the sun is more pleasant on a cold winter day than standing in shade. Is the temperature of air in the sun considerably higher than that of the air in shade?
Yes. The temperature in an open place will be higher than that of a shady place due to the presence of more number of heated molecule in the former case.
Human body needs thermal comfort despite the surrounding condition. On a cold environment, human body needs to transfer less amount of heat compared to that in a normal environment.
The temperature of the surrounding is lower than the usual temperature on a winter day, and human body will transfer more heat to surrounding by radiation, convection and conduction*, causing a drop in the temperature of the outer skin. In an open space, where there is more radiation from sun, the temperature of the surrounding will be comparatively higher than a shady place. So, the heat transfer from human body will be lower in the open space since all the above modes of heat transfers are directly proportional to the Temperature difference between human body and the surroundings.
In the case of shady place, the temperature of the surroundings will be comparatively lower due to 2 reasons;
1. There is lesser availability of direct radiation from the sun
2. The phenomenon of transpiration** from the leaves of the trees will give a cooling effect.
So, there will be a higher amount of heat transfer from human skin to the colder surroundings.
To conclude, on a winter day, a hot environment will be convenient in order to reduce the heat transfer from the body.
*There are other types of heat transfer such as the heat transfer caused by Breathing, etc.
**Transpiration is the process of removal of water from leaves through the pores called Stomata. The evaporation of this will cause a cooling effect.
Rate this question :
Cloudy nights are warmer than the nights with clean sky. Explain.HC Verma - Concepts of Physics Part 2
Two identical metal balls one at T1 = 300 K and the other at T2 = 600 K are kept at a distance of 1m in vacuum. Will the temperatures equalize by radiation? Will the rate of heat gained by the colder sphere be proportional to as may be expected from the Stefan’s law?HC Verma - Concepts of Physics Part 2
On a cold winter night you are asked to sit on a chair. Would you like to choose a metal chair or a wooden chair? Both are kept in the same lawn and are at the same temperature.HC Verma - Concepts of Physics Part 2
On a hot summer day we want to cool our room by opening the refrigerator door and closing all the windows and doors. Will the process work?HC Verma - Concepts of Physics Part 2
Standing in the sun is more pleasant on a cold winter day than standing in shade. Is the temperature of air in the sun considerably higher than that of the air in shade?HC Verma - Concepts of Physics Part 2
The temperature of the atmosphere at a high altitude is around 500°C. Yet an animal there would freeze to death and not boil. Explain.HC Verma - Concepts of Physics Part 2
An ordinary electric fan does not cool the air, still it gives comfort in summer. Explain.HC Verma - Concepts of Physics Part 2
A heated body emits radiation which has maximum intensity near the frequency v0. The emissivity of the material is 0.5. If the absolute temperature of the body is doubled.HC Verma - Concepts of Physics Part 2
A hot liquid is kept in a big room. The logarithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly.HC Verma - Concepts of Physics Part 2
Why does blowing over a spoonful of hot tea cools it? Does evaporation play a role? Does radiation play a role?HC Verma - Concepts of Physics Part 2