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WEEK 5:
TOPIC: HEAT ENERGY
CONTENT:
- Temperature and its measurement, liquid-in-glass thermometer.
- Constant volume gas thermometer
- Resistance thermometer and Thermocouple.
SUB-TOPIC 1: Temperature and its measurement, liquid-in-glass thermometer.
TEMPERATURE AND ITS MEASUREMENT
Temperature is a measure of the degree of hotness or coldness of a body. It is measured by means of a thermometer. The S. I. Unit of temperature is the Kelvin. However, it is also measured in degree Celsius.
THE THERMOMETER
The thermometer is the instrument used for measuring temperature. There are various types of thermometer, e.g. liquid-in-glass thermometer and the thermocouple. Each one makes use of the change in the physical properties of materials they are made of, to indicate temperature change.
- The liquid-in-glass thermometer. The liquid-in-glass thermometer uses liquid(mercury) as thermometric substance. In which the change in volume of the liquid measures the change in temperature. Any liquid that will be used as a thermometric liquid must be a good conductor of heat, be easily seen in glass, have a high boiling point, have a low freezing point, have a low specific heat capacity, must not wet glass and must expand uniformly. The liquid-in-glass consists of the school thermometer, clinical thermometer, maximum and minimum thermometer.
- The clinical thermometer has a constriction and it has a short range (350C – 430C). The narrow constriction prevents the mercury from flowing back into the bulb immediately after the thermometer has been removed from the patient’s body.
Constriction
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