Ordinary mercury in glass thermometer is used for measuring temperature upto 120

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Question
Ordinary mercury in glass thermometer is used for measuring temperature upto 120�C. However, for measuring higher temperature upto __________ �C, thermometer is made by filling nitrogen under pressure above the mercury, which stops the evaporation of mercury and reduces the chance of broken thread of mercury.
Options
A. 250
B. 350
C. 550
D. 700

Correct Answer

550

Process Control and Instrumentation problems

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1. Dome temperature of blast furnace stove is most accurately measured by a
Options
A. radiation pyrometer.
B. platinum-platinum/rhodium ther-mocuple.
C. iron-constantan thermocouple.
D. platinum resistance thermometer.

2. Which of the following instruments is not used for measuring sub-zero (<0�) temperatures?
Options
A. Platinum resistance thermometer
B. Mercury in glass thermometer
C. Vapor pressure thermometer
D. Radiation pyrometer

3. Mercury thermometer is commonly used for low temperature measruement. The freezing point and boiling point of mercury are respectively __________ �C.
Options
A. - 39 and 350
B. - 51 and 439
C. - 79 and 395
D. - 10 and 425

7. Emf developed by a thermocouple while measuring a temperature of 800�C is about 31 mV. The type of thermocouple used is
Options
A. chromel-alumel
B. iron-constantan
C. platinum-platinum+rhodium
D. none of these.

10. Temperature of molten pig iron (1450�C) and molten slag (1500�C) flowing out of a blast furnace is measured by a/an
Options
A. chromel-alumel thermocouple
B. optical pyrometer
C. radiation pyrometer
D. either (b) or (c)

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