Gujarati -Std-7 Class work in Work book 28/02/2017
Science Class 7 : Heat and its Transfer
Heat and Its Transfer Q1 You may have noticed that a few sharp jerks are given to clinical thermometer before using it. Why is it done so? Ans. The jerk to the thermometer will allow the mercury in or above the kink to flow into the bulb so that the mercury level falls below 35 degree Celsius Q2 Why is it advised not to hold the thermometer by its bulb while reading it? Ans. If we hold a thermometer by its bulb, the mercury level will change to show the temperature of our hand and the desired reading will not be observed. Q3 At a camp site, there are tents of two shades one made with black fabric and the other with white fabric. Which one will you prefer for resting on a hot summer afternoon? Give reason for your choice. Would you like to prefer the same tent during winter? Ans. On a hot summer afternoon, the tent made up of white fabric, will be preferred as white colour is a bad absorber and good reflector of
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