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the measure of
the hotness or the coldness
of a body
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Temperature is measured in ...
Kelvin and Celsius
SI unit Practical
unit
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Symbols Kelvin Celsius
T t or
T / K t / °C
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Relationship … Kelvin and Celsius
t / °C = T / K - 273.15
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Thermometers measure temperature.
Thermometric Property
• A physical property
• that changes measurably
• with temperature
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Thermometric Property - Examples
• e.m.f. of a thermocouple
• pressure of a gas at constant volume
• volume of a gas at constant pressure
• resistance
• Length of a liquid column
• colour
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Thermometric Property - Examples
• Length of a liquid column
L
Mercury-in-glass thermometer
Alcohol-in-glass thermometer
Laboratory thermometer
Clinical thermometer
(Barometer) / Thermometer
+ 3 5 7 ° C
+ 7 8 ° C
- 3 9 ° C
- 1 1 5 ° C
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Thermometric Property - Examples
• e.m.f. of a thermocouple
Infra-red
Car engine temperature(but …)
- 200 °C to 1700 °C
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Thermometric Properties
Volume increases
measurably
with temperature
Volume of a gas at constant pressure
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Pressure increases
measurably
with temperature
• Pressure of a gas at constant volume
C o n s t a n t V
o l u me
G a s T h
e r m o me te r
Thermometric Property - Examples
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Thermometric Property - Examples
• Resistance Metal (Platinum)
Thermistor (Semiconductor)
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Using A Thermometric Property
To Measure Temperature
In pure
melting
ice
In steam
above
boiling water
Mark ...
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Using A Thermometric Property
To Measure Temperature
L ICE
L STEAM
0°C 100°C
Length
L
Warm water temp. = ??
Measure L …
Calculate
from graph
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Using A Thermometric Property
To Measure Temperature
0°C 100°C
Resistance
R
Warm water temp. = ??
Measure R …
Calculate
from graph
R ICE
R STEAM
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55.3 ° … using the Mercury thermometer
55.7 °C … using the Resistance thermometer
Temperature of the warm water =
The different thermometric propertiesvary differently with temperature.
All agree at … 0 °C and 100 °C
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A standard thermometer is needed.
In school lab.
… a mercury-in-glass thermometer
Calibrate other thermometers using this.
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Clinical Thermometer
“Fever Strip ..”
Liquid Crystals
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Provides accurate and rapid
temperature readings from the ear
within three seconds.
Measures the temperature of the
infrared heat given by the eardrum
and surrounding tissues
Infra-Red Radiation
Thermometer
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Thermocouple
- DataStudio
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Bimetallic Thermometers
Oven Refrigerator
Lab.
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Boiler Thermometer
• Thin copper pipe
• “Santotherm” expands
• Pressure on diaphragm
• Turns needle
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Car - Temperature Gauge
Thermistor (or Thermocouple)
Platinum Resistance Thermometer
Thermocouples
Constant Volume Gas Thermometer (Standard)
Optical Pyrometers
To Plot The Calibration Curve Of A Thermometer Using
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To Plot The Calibration Curve Of A Thermometer Using
The Laboratory Mercury Thermometer As A Standard
APPARATUS
Alcohol thermometer (on metre stick)
Mercury ThermometerBeaker & water, etc.
To Plot The Calibration Curve Of A Thermometer Using
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To Plot The Calibration Curve Of A Thermometer Using
The Laboratory Mercury Thermometer As A Standard
PROCEDURE
1. Heat gently
… take readings every 10°
2. Measure (2)
… Length of .. & Temperature
3. L = ?
Temperature from mercury thermometer
4. Repeat, every 10°, to graph.
To Plot The Calibration Curve Of A Thermometer Using
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To Plot The Calibration Curve Of A Thermometer Using
The Laboratory Mercury Thermometer As A Standard
RESULTS Length
Temperature
PRECAUTIONS
1. Heat gently … thermal equilibrium2. Etc.
Calibration Curve - Measuring Temperature With It
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Calibration Curve Measuring Temperature With It
Length
Temperature
L
L
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Absolute Zero - 273.15 °CFreezer
Fridge / Ice-box - 4 °C
Water Freezes
Fridge - Main+ 20 °CRoom Temp.
Body Temp.
- 18 °C
0 °C
+ 4 °C
+ 37.0 °C
Water Boils +100 °C
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Alcohol freezesAlcohol boils + 78 °C
Mercury freezes - 39 °C
Mercury boils + 357 °C
Chips
Horse
Bunsen flame + 1500 °C
Filament + 2500 °C
- 115 °C
+ 200 °C
+ 38.3 °C
Sun’s surface + 6000 °C
H-bomb / A-bomb Millions
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