Page 53 - Science Class 6 Times Publication

It consists of a capillary tube with a narrow bore. The capillary tube
is swollen to a bulb at one end and is sealed at the other end. The bulb

is lled with alcohol. There is a cover of glass outside the capillary
tube. The outer cover is graduated in degree from -10°C to 110°C.
When the bulb comes in contact with a body whose temperature is
to be measured, there may be rise or fall of the level of alcohol in the
capillary tube. After sometime, the level of alcohol remains  xed.
The level of alcohol gives the temperature of the object.

Clinical thermometer

It is a thermometer which is used to measure temperature of a human body.

A clinical thermometer consists of a capillary tube with a  ne bore.
One end of the capillary tube is swelled to a bulb. The bulb is  lled
with mercury. Another end of the tube is sealed. There is a narrow
constriction in the capillary tube near the bulb. The capillary tube
is covered by a glass cover. The glass cover is graduated in degrees
from 35° to 42°C or 94°F to 108°F.

When we have to measure temperature of a human body, we keep
the bulb of thermometer in the armpit or mouth. There occurs rise in
the level of mercury and reading is obtained. When the thermometer
is taken out from the body, the temperature decreases. But, the level
of mercury does not return to the bulb due to the constriction present
in the capillary tube. This helps to take correct reading. After its use,
the thermometer is jerked to return the mercury to the bulb.

Times' Crucial Science and Environment 49 Book 6