Question

What does the bulb of a clinical thermometer contain?
A. water
B. mercury
C. iron
D. zinc

Answer 1

Hint: Thermometer is a device used to measure the temperature of the body. It consists of a bulb at one end followed by a long strip on which the readings are marked. The bulb contains a liquid. The liquid should have a very high boiling point.

Complete step by step answer:
Thermometer is a device used to measure the temperature of the body. It consists of a bulb at one end followed by a long strip on which the readings are marked. The bulb contains a liquid. The bulb of a clinical thermometer contains mercury.
Hence, the correct option is B.

Additional Information:
Physical property a substance plays an important role in the construction of a thermometer. In a mercury thermometer, principle of expansion of mercury with rise in temperature is used. The platinum thermometer is based on the principle of the change in resistance with change in temperature.
Thus for a construction of a thermometer, proper choice of substance, whose physical property varies uniformly with rise in temperature is essential.
When a thermometer is constructed, it should be properly calibrated. Standard fixed points are selected for calibrating a thermometer. Melting point of ice, boiling point of water, melting point of silver, melting point of gold are taken as fixed points.
The thermometer should be able to detect small changes in temperature. It should show the temperature of a body in a short time. It should not take a large quantity of heat for its own heating from the body whose temperature is being measured.

Note: Points essential for a substance present in the bulb of the thermometer.
(i) It should have a very high boiling point.
(ii) it should not absorb a large amount of heat from the body that is being measured.
(iii) it should show large changes for small changes in temperature.