Research laboratory work in physics

CLOTHING AS THERMAL INSULATION The problem under study: how to choose clothes for light physical exertion at home, depending on the air temperature in the room, in order to provide a feeling of comfort, if the thermal insulation properties of clothing are known? Read the text! One of the means of adaptation to the thermal environment is clothes. When choosing the type of clothes, it is possible to compensate for individual sensitivity to air temperature. Clothes made of smooth fiber canvases that have a larger area of contact with the body do not have sufficient heat-insulating properties. Such clothes also have low hygroscopicity. If such clothes are wet, then their thermal conductivity increases, since the heat capacity of water is large. Wetting of silk and similar synthetic fabrics, as well as cotton fabrics, significantly reduces their heat-insulating properties. The springy fibers of wool retain up to 60% of the air in their strands when wet, and therefore wool products retain heat in large measure. There are common traditions of dressing at work and at home, which affect the desired air temperature. In comfort conditions, the skin temperature should be 33.3 C. In linen and semi-woolen or woolen clothes at rest, the desired air temperature is 21 C. When moving under light physical exertion, the temperature should be lower (18 C). Heat and cold sensitive receptors are located in the skin. Heat receptors are located deeper than cold receptors, the number of which is greater. Of great importance is the summation effect. Irritation of large areas leads to a decrease in the sensitivity threshold. Heat receptors record temperature changes between 20 and 47 C, but with the greatest intensity -- 38...43 C range. Cold receptors are active 10...40 C in the range with a maximum intensity of 20...34 C in the temperature interval. In this way, the body receives information about the temperature of the skin and its changes. Reflector responses to cold signals focus on heat retention. The blood vessels of the skin narrow, so the heat output decreases even up to 33 %. As a result of further cooling, muscle activation occurs, and later - externally pronounced trembling of the body. This happens even before the temperature drops in deeper tissues. If the temperature rises, then the rate of enzymatic reactions increases. At a temperature of +40 C, on the other hand, proteins and lipids undergo changes so that they become unsuitable for tissue cells. As the temperature rises, reflex reactions begin, which dilate the blood vessels of the skin. As blood circulation in the skin increases, thermal conductivity increases 5...6 times. If the temperature balance does not normalize, then the skin temperature rises. With an increase in skin temperature to 30...32 C, the release of sweat began. Task imagine that you have a possible task! Imagine you have a chance a) wear clothes of different materials-polyester, cotton, flax, semi-Wool, Wool, in addition, with short and long sleeves; b) change the air temperature in the room from 15C to 25C with the radiator regulator; c) measure air temperature, air humidity, human skin temperature, time! Put forward the hypothesis of the study, choose dependent, independent and fixed quantities/features, as well as the necessary measuring devices and develop a description of the course of the study! Performs Data Processing!

Student's worksheet Hypothesis ..................................................................................................................................................................................................... ..................................................................................................................................................................................................... ..................................................................... Sizes Addicts - Independent - Fixed - Work accessories

Progress of work: 1. 2.

Recording and processing of the data obtained :

Analysis, evaluation and conclusions of the results :