1
Question
why a clinical thermometer can't be sterilized with hot boiling water. What is the working principle of a thermometer.
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Solution
Dear student,
The glass is a poor conductor of heat and expands on heating. When a thermometer is placed in boiling water, the mercury is heated up and it, in turn, heats the inner portion of the glass. The layer of glass is thick and as it is a poor conductor of heat, the outer portions of the thermometer are not heated. Therefore, the inside layer of glass expands but not the outer layer and hence it breaks.
Principle of a thermometer: A simple thermometer is basically a thin cylinder which is calibrated and consists of a liquid typically water, mercury or some alcohol inside it. The markings are made on the outside and the min. and max. is determined by the thermometer usage.
In general, Most thermometers work on the principle that elements and compounds expand as their temperature increases. Liquids or solids that expand at a constant rate over the desired temperature range are used so that the amount they have expanded can be measured and compared against known expansion rates to determine the temperature.
Regards
The glass is a poor conductor of heat and expands on heating. When a thermometer is placed in boiling water, the mercury is heated up and it, in turn, heats the inner portion of the glass. The layer of glass is thick and as it is a poor conductor of heat, the outer portions of the thermometer are not heated. Therefore, the inside layer of glass expands but not the outer layer and hence it breaks.
Principle of a thermometer:
A simple thermometer is basically a thin cylinder which is calibrated and consists of a liquid typically water, mercury or some alcohol inside it. The markings are made on the outside and the min. and max. is determined by the thermometer usage.
In general, Most thermometers work on the principle that elements and compounds expand as their temperature increases. Liquids or solids that expand at a constant rate over the desired temperature range are used so that the amount they have expanded can be measured and compared against known expansion rates to determine the temperature.
Regards
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