The definition of thermometer and temperature.
• Thermometer is a tool to measure temperature of an object
• Temperature is the degree of hotness and coldness of an object
A thermometer consists of :
1.A long glass tube has scale
2.Capillary pipe
3.Liquid ( mercury or alcohol )
4.The upper part is vacuum
Kinds of thermometer
There are four kinds of thermometer based on the scale :
1.Celcius scale thermometer : 0oC-100oC
2.Reamur scale thermometer : 0oR-80oR
3.Fahrenheit scale thermometer : 32oF-
212oF
4.Kelvin scale thermometer : 273oK-
373oK
To Compare scales of thermometer
• C : R : F = 100 : 80 : 180
• C : R : F = 5 : 4 : 9
The equation used to convert the scale:
▪ C scale to R scale : T0R=4/5T0C
• R scale to C scale : T0C = 5/4 T0R
• C scale to F scale : ToF = 9/5 ToC + 32
• F scale to C scale : ToC= 5/9 ( ToF – 32 )
• C scale to K scale : ToK = ToC + 273
The liquids are use as a thermometer filler is :
• Mercury and Alcohol
The weaknesses of mercury
1. Its price is very high
2. It cannot measure very low temperature ,because its freezing point is – 40oC
3. Mercury is poisonous
The Superiorities of Mercury
1.It is visible , because its silvery shining
2.Its expansion is regular
3.It can measure a high temperature
4.It does not make wet the wall of its
place .
5.It can measure the temperature quickly
and precisely
The weaknesses of alcohol
• It cannot measure a high temperature.
• It makes wet the wall of its place
• It is colourless
The Superiorities of alcohol
• It can measure a low temperature.
• It can measure the temperature precisely
• Its expansions is regular
The upper fixed point of
• Celsius,Reamur,Fahrenheit and Kelvin thermometer is the temperature of boiling water
The lower fixed point of
• Celsius thermometer is the temperature of melting ice.
• Fahrenheit thermometer is the temperature of the mixture of ice and salt
EXERCISE
1. The temperature of matter measured by Reamur thermometer is 60o. If it is measured by Celsius Thermometer its temperature becomes……..
2. The temperature of a body measured by Celsius thermometer is -40o. If it is measured by Fahrenheit Thermometer, its temperature becomes……..
3 .What is temperature ?
4 . The temperature of an object is 27oC
What is the temperature when it is
measured in Kelvin?
5 . The temperature of an object is 400ºK
What is the temperature when it is
measured in Celsius?