Sunday 6 December 2009

Physics unit 1 - Temperature

Definition: It’s a physical quantity that measures the degree of hotness or coldness of an object. The unit is degree Celsius. (˚C) Temperature scale can be defined by an upper fixed point, lower fixed point and dividing scale. The pair of fixed point should be easily obtained and reproducible, therefore we define the lower fixed point as the temperature of pure melting ice at 1 apm (standard atmospheric pressure) and the upper fixed point as the temperature of pure boiling water at 1 apm. Calibration of thermometer (to mark the thermometer) : Put it into pure melting ice (lower fixed point) followed by the pure boiling water. Liquid level is recorded in each case and the separation between the two markings is divided into 100 equal divisions. Each division represent 1˚C. Thermometric properties: of a matter is a measureable physical quantity of the matter which changes along with the temperature. For example, density. Thermometer: a device with measurable property which changes with temperature. Liquid-in-glass thermometer consist of a narrow glass tube, one end consists a bulb that contains liquid (alcohol or mercury). When temperature rises, liquid expands and rises in the tube. Oppositely they contract and fall in cooler temperature. If the length of liquid in the tube changes more in a given quantity of temperature change, then we say it has a higher sensitivity. Clinical thermometer has an extra constriction between the bulb and the tube to prevent the mercury flowing back to the bulb. Temperature in terms of molecular motion It is the measure of the average kinetic energy due to the random motion of the molecules of the object. Equal temperature means equal average kinetic energy. missed table: 1)temperture scale 2)Liquid-in-glass themometer 3)Different kinds of thermometer Available for the .doc file! (F.4 -> Physics)

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