Thermometer

1. ThermometerThermometer
PHYSICS  MODULE 3
UNIT 1  LESSON 2
BEGIN

2. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Introduction
Answer the following questions and then participate in a class discussion
about temperature. Type your responses in the box titled “Answers”.
1. How hot is boiling water?
2. How cold is water that is frozen?
3. What does ‘room-temperature water’
mean?
4. What is the S.I. unit for measuring
temperature?
5. What is the instrument used to measure
temperature?
6. Can we use our hand to measure
temperature instead of an instrument?
7. When have you used a thermometer?
8. Have you ever used one when you were
sick?
Possible Answers
1.1000
C
2.00
C.
3.250
C.
4.Kelvin.
5.Thermometer.
6.No.
7.Various answers
such as “when I was
ill with fever”.
8.This answer may
vary according
individuals.
Click here to check
answers

3. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Objectives
As a result of this lesson, the student will be able to:
state the use of a thermometer;
discuss the different types of thermometers;
explain reasons for the use of a thermometer;
measure the temperature of a substance by a clinical and laboratory
thermometer to the nearest degree Celsius;
describe the physical changes that occur in a thermometer with
increasing or decreasing temperature;
work independently and with others.
willingly participate in class discussions

4. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
1 - Types of Thermometer
There are several types of thermometers:
Laboratory thermometer
Clinical thermometer
Thermocouple
Bimetallic Strip
Pyrometers
Thermistor (Resistance thermometer).

5. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Laboratory thermometer
 The Laboratory thermometer is an
example of liquid in glass
thermometer. It is mercury or alcohol
filled thermometer that ranges from
-20 to 1100C. It is normally used in
simple laboratory experiments where
temperature is measured.
 In a Laboratory thermometer the
volume of the liquid changes when
the temperature changes ;when the
temperature increases the liquid
expands (larger volume).

6. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Laboratory thermometer (cont’d)
The table below shows the temperature range of several liquid in glass
thermometer. Why are mercury thermometers mostly used rather than
alcohol thermometers?
Liquid Temperature range, °C
Lowest Highest
Ethanol -80 70
Mercury -35 650
Toluene -90 200
Kerosene -60 300
Pentane -200 20
Petroleum
Ether
-120 25
Answer:
1.Mercury is a naturally opaque liquid
(Silver).Thus it can be easily seen.
2.Mercury does not wet glass.
3.Mercury is a liquid metal. Thus it has high
conductive properties that allow it to be more
sensitive than the alcohol in glass thermometer.
Click here to check answers

7. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Clinical thermometer
The Clinical thermometer measures human body temperatures.
It has limited scales (34-50oC) and constriction. It is more accurate and will
give an exact temperature.
stem
bulb
overload capacity
scale etched on glass
small bore
partial immersion line
range supression cavi
bulb
maximum indication
constriction

8. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Thermocouple
 Thermocouple: This is a thermometer that uses
electricity (electromotive force) to measure
temperature. It consists of two dissimilar metals,
such as iron and constantan alloy wires joined at
two points (junctions). The measuring junction or
‘hot junction’ is inserted into the medium where
the temperature is to be measured.
Thermocouples are used to measure very high
temperatures.
 Taken from
http://chemrat.com/ChemHog2/Industrial
%20Control%20Systems_files/THERM05.DOC

9. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Bimetallic Strip
 Bimetallic Strip : This thermometer
consists of two different metals
bonded together that expand and
contract in different amounts by the
variation of temperature. They are
mainly used in thermostats to control
room temperature.
 Taken from
http://chemrat.com/ChemHog2/Indu
strial%20Control
%20Systems_files/THERM05.DOC
HELICAL
BIMETALLIC STRIP
FLAT
BIMETALLIC STRIP
Fixed End
Free end
high expansion
coefficient
coefficient
low expansion
Fixed End
Free end
connected to
rotating dial
bulb

10. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Pyrometers
 A pyrometer is simply a thermometer
which is commonly used as an instrument
for measuring temperatures beyond a
thermocouple range. It is based on
electromagnetic radiation( all hot bodies
will emit radiant energy whose intensity
depends upon the absolute temperature
of the emitting surface).
 Taken from
http://chemrat.com/ChemHog2/Industrial
%20Control
%20Systems_files/THERM05.DOC

11. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Thermistor (Resistance thermometer)
Thermistor (Resistance thermometer). This thermometer consists of a pure
metal wire that measures temperature of substance by a change in its
resistance. It normally uses platinum wire in its construction, but copper,
nickel and rhodium alloy may also be used in various temperature ranges.
Thermistor

12. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Activity 1
The teacher will demonstrate to students how to use a thermocouple and
a thermistor in the measurement of temperature.
Thermistor

13. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
2 - How do you read a thermometer
1. What is the temperature
reading on the thermometer?
Answer:
1.Shake the thermometer to get liquid
below the bend.
2.Place it under the tongue or armpit of
patient.
3.Wait for a few minutes.
4.Remove from patient and read
temperature.
100.20
F
2. How would you use a clinical
thermometer?
CHECK
Click here to check answers

14. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
2 - How do you read a thermometer (cont’d)
The steps to follow in reading a thermometer:
Place the container with the liquid to be measured on the flat surface.
Hold on the tip of thermometer (do not hold bulb of thermometer).
Your eyes must be in line with the observed point.

15. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
3 - Liquid in Glass Thermometers
The parts of a liquid in
glass thermometer.
Column of vacuum space
Measured temperature
Capillary tube
Thermometer scale
Bulb with liquid
Liquid thread

16. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
3 - Liquid in Glass Thermometers (cont’d)
Accuracy Requirements for Liquid-in-Glass Thermometers
a)A large constant coefficient of thermal expansion of the fluid
b)Adhesion of the fluid to the glass must be very low
c)The fluid level must be clearly visible
The fluids freezing and boiling points must satisfy the desired range of use
Sensitivity is the ability of a thermometer to identify small changes in
temperature which depends on the size of the thermometer bulb and
conductivity of the liquid. A decrease in the bulb size will improve
sensitivity.

17. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
QUIZ
 Are you ready to test yourself?
 There are five multiple choice items that you are required to do.
 For each item, click on the letter of the correct response and then
click the button ‘NEXT QUESTION’ to continue.
 Click the BEGIN QUIZ button to start doing the quiz.
BEGIN QUIZ!BEGIN QUIZ!

18. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
QUIZ: Question 1
Mercury is used in thermometers above 100 °C rather than alcohol
because mercury has a higher_________.
A. Melting point
B. Freezing point
C. Density
D. Boiling Point
FEEDBACKFEEDBACK

19. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Quiz: Feedback to Question 1
Mercury is used in thermometers above 100 °C rather than alcohol
because mercury has a higher boiling point.
NEXT QUESTIONNEXT QUESTION
The correct answer is D. The boiling point of alcohol is less than
100 °C. while mercury has a boiling point far above 100 °C.
Hence mercury is used in thermometers above 100 °C rather
than alcohol.

20. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
QUIZ: Question 2
Alcohol in glass thermometers are employed in very cold countries such as
Alaska and Canada because alcohol has a______
A. red colour
D. High melting
C. high boiling point
B. low freezing point
FEEDBACKFEEDBACK

21. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Quiz: Feedback to Question 2
Alcohol in glass thermometers are employed in very cold countries such as
Alaska and Canada because alcohol has a low freezing point .
NEXT QUESTIONNEXT QUESTION
The correct answer is B.
Alcohol freezes below -99 °C, hence it is employed in very cold
countries such as Alaska and Canada.

22. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
QUIZ: Question 3
Which one of the following thermometers has a constriction at one end?
A. Thermocouple thermometer
D. Thermistor Thermometer
B. Laboratory thermometer
C. Clinical Thermometer
FEEDBACKFEEDBACK

23. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Quiz: Feedback to Question 3
Which one of the following thermometers has a constriction at one end?
NEXT QUESTIONNEXT QUESTION
The correct answer is C. The Clinical thermometer is the only
thermometer with a constriction because of how it is used.

24. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Quiz: Question 4
What is the most suitable temperature range for a clinical thermometer?
A. 0 o
C to 42 o
C
D. 42 o
C to 100 o
C
C. 35 o
C to 100 o
C
B. 35 o
C to 42 o
C
FEEDBACKFEEDBACK

25. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Quiz: Feedback to Question 4
What is the most suitable temperature range for a clinical thermometer?
NEXT QUESTIONNEXT QUESTION
The most suitable temperature range of a clinical thermometer
is “B”, 35 o
C to 42 o
C. An example of a typical thermometer:

26. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
QUIZ: Question 5
What is the reading of thermometer in the diagram?
B. 70 o
C
D. 22 o
C
C. 71o
C
A. 20 o
C
FEEDBACKFEEDBACK

27. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
Quiz: Feedback to Question 5
What is the reading of thermometer in the diagram?
The most suitable reading on the thermometer is 20 o
C .
END OF QUIZEND OF QUIZ

28. OBJECTIVES
Types of
Thermometers
Reading a
Thermometer
Liquid in Glass
Thermometer
QUIZINTRODUCTION
X
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