This document discusses temperature and its measurement. It defines temperature as a measure of hotness or coldness, while heat is a form of energy that can transfer between bodies with different temperatures. There are several types of thermometers discussed for measuring temperature, including mercury-in-glass, gas, thermoelectric, and resistance thermometers. Gas and resistance thermometers provide the widest measurement ranges, from -270°C to 1500°C and -180°C to 1520°C respectively. The document also provides examples of converting between Celsius, Fahrenheit and Kelvin temperature scales.

1. PHYSICS
TEMPERATURE AND ITS
MEASUREMENT
Short revision series

2. What is temperature? What is heat?
 Temperature is measure of degree of hotness
or coldness of a body
 Heat, however, is a form of energy that is
transferable from one body to another as a
result of temperature difference between the
2 bodies.

3. HEAT TEMPERATURE
Form of energy Measure of coldness or hotness
of a body
Can flow from a body of higher
temperature to another of colder
temperature
Does not flow
Cant be measured, but
calculated
Can be measured with a
thermometer
Unit in J K, 0C, 0F
Can do work Cannot do work

4. How do you measure
temperature?
 Thermometres
 Types
 Mercury-in-glass
 Gas
 Thermoelectric
 Resistance

5. Mercury-in-glass
 Measures temperature at the range of -390C
to 3560C
ADVANTAGES DISADVANTAGES
Easily read because of its
opaque colour
Not suitable for measuring
temperature lower than -390C
Does not easily evaporate Not very accurate
Responds rapidly to
temperature changes due to
its conductivity
Fragile

6. Gas thermometres
 Eg constant volume gas thermometre
 Range = -2700C to 1500 0C
ADVANTAGES DISADVANTAGES
Very accurate Cumbersome; cant be used
to measure small vol liquids
Highly sensitive Requires knowledge of
pressure at fixed points
Wide range
Useful in callibrations of
other thermometres

7. Gas thermometres cont.
 Scale θ0C = Pθ – P0 x 100
P100 – P0
Pθ = Pressure at temperature θ
P0 = Pressure at 00C
P100 = Pressure at 1000C
 A constant vol gas thermometre records
pressure of a body at 200mmHg at 00C and
300mmHg at 1000C. What is the
temperature when it reads 250mmHg?

8. Gas thermometres cont.
 Using the scale equation
 Temp θ = Pθ – P0 x 100
P100 – P0
 = 250 – 200 x 100 = 50 x 100 = 500C
300 – 200 100

9. Thermoelectric thermometres
 Range = -2500C to 11550C
 Uses the principle of thermocouple which
consists of 2 different metals copper and
constantan, or copper and iron, or iron and
constantan joined at one end and connected
to a galvanometre which measures current
flow
 This current depends on the temperature
difference between the cold and hot ends.

10. Thermoelectric thermometres
cont.
ADVANTAGES DISADVANTAGES
Wide range Affected by any change
in flow of current
Very sensitive

11. Resistance thermometres
 Range = -1800C to 15200C
ADVANTAGE DISADVANTAGE
High accuracy and
wide range
Not suitable for
measuring rapid
tempearture
changes because it
requires time to
attain thermal
equilibrum with its
sorrounding

12. Resistance thermometres
 Scale = θ0C = Rθ – R0 x 100
R100 – R0
 Eg: What is the temperature when a
platinum resistance thermometre measures
3 Ω if the resistance measured at 00C is 2 Ω
and 4 Ω at 1000C?

13. Resistance thermometres cont.
 Rθ – R0 x 100
R100 – R0
 3 – 2 x 100 = ½ x 100 = 500C
4 – 2

14. Converting one temperature scale to
another
 C = F – 32 = K – 273
100 180 100
Also F = 9/5 C + 32
 Eg: Convert 300C to F and K

15.  C = F – 32
100 180
 30 = F – 32
100 180
100(F -32) = 5400
F-32 = 54
F = 54 + 32 = 860F

16.  C = K – 273
100 100
 30 = K – 273
100 100
100(K – 273) = 3000
K = 30 + 273 = 303K

17. END