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Temperature: It is a measure of the average kinetic energy of the atoms or molecules in a body. (It tells us how hot or cold something is.)
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Heat: Heat is the energy that is exchanged between two objects due to their difference in temperature.
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Calibrating a thermometer:
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Step 1: To measure temperature we need a physical quantity that is affected by temperature. For example volume, e.m.f., resistance or pressure.
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Step 2: Mark 0oC (using pure melting ice) and 100oC (by placing just above boiling water).
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Step 3: Divide the temperature range between the two marks into 100 equal parts.
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Thermometric liquids:
Mercury
Alcohol
Advantages
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Good conductor
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Does not wet glass
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High boiling point
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Not poisonous
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Cheap
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Low freezing point
Disadvantages
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Poisonous
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Expensive
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High freezing point (-39oC)
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Bad conductor
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Wets glass
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Low boiling point (78oC)
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Some definitions:
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Responsiveness: It is about how quickly you get the result.
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Sensitivity: It is about how much does the thermometric property (e.g., volume) change per degree change in temperature.
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Range: The minimum and maximum temperatures that can be measured.
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Linearity: It is about whether each degree is an equal distance or not.
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Liquid-in-glass thermometers: In comparison to a laboratory thermometer, a clinical thermometer has:
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a constriction
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less range
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greater sensitivity (divisions further apart)
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triangular cross-section (for magnification)
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Thermocouple thermometers:
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Construction: You should be able to draw figure 8.13.
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Defining equation: e.m.f. = Δ θ
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Advantages:
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Large range
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Measures temperature at a point
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High responsiveness
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Can be connected to computers because of electrical output
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