Elenco Solar Energy - Manual (Page 4)

3
Experiment no. 1 The thermometer
There are many types of thermometers; the one enclosed in your kit is the most
common kind. It contains a bulb of liquid at one end and a long thin bore which runs
up the center of the glass tube. When the liquid in the bulb is heated, it expands and
moves up the bore; when it is cooled, it moves down.
To determine the temperature we see how far the liquid has moved up or down
the bore and read off the temperature from the plastic base.
The scale of your thermometer is calibrated in both the Celsius and Fahrenheit scales.
The Celsius (sometimes referred to as
Centigrade) scale is the one most commonly
used in scientific work. On the Celsius scare
0
o
is the freezing point of water and 100
o
is
the boiling point of water. The range between
the freezing and boiling point of water is divided
into 100 equal parts of degrees. Degrees Celsius
are written as
o
C.
The United States still uses the Fahrenheit
scale of temperature, you will very often come
across this unit of temperature measurement.
In the Fahrenheit scale water freezes at 32
o
and boils at 212
o
. The temperature range
between the freezing and boiling point of water
is divided into 180 equal parts of degrees. The
common abbreviation for a degree Fahrenheit
is
o
F.
There is one other temperature scale which
is in common use in more advanced scientific
work; it is the Kelvin scale. Knowing that a
gas when cooled one degree centigrade loses
1/273 of its pressure, Lord Kelvin reasoned
that at 273
o
C below zero –absolute zero – a
gas would not have any pressure. He devised
a scale where 0
o
K is that theoretical point
where gases do not exert any pressure and
each degree is identical to a degree centigrade.
Included here you will find a comparative
chart of all these temperatures.
-60
-40
-20
0
20
40
60
80
100
120
140
160
180
200
220
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
100
110
370
380
TEMPERATURE SCALE CONVERSION
FAHRENHEIT- CENTIGRADE- KELVIN
water boils
human body
temperature
room temperature
water freezes
WARNING: Your thermometer is only capable of measuring up to 50
o
C.
Make sure that you do not leave it in boiling water, which is 100
o
C,
or 212
o
F.