Test: Thermocouples - GATE MCQ

Operation of thermocouple is governed by _______________.

______________ describes current flow between two junctions formed by two different metals.

An egg with a mean diameter of 4 cm and initially at 25 degrees. Celsius is placed in an open boiling water container for 4 minutes and boiled at a particular level. For how long should a similar egg boil at the same level when the refrigerator temperature is 5 degrees Celsius? Use lumped parameter theory and assume the following properties of egg

k = 12 W/m K

h = 125 W/m2 K

c = 2 k J/kg K

p = 1250 kg/m3

“The response of a thermocouple is defined as the time required for the thermocouple to reach the surrounding temperature when it is exposed to it.”

A person is found dead at 5 pm in a room whose temperature is 20 degrees Celsius. The body temperature is measured to be 25 degrees Celsius when found. The heat transfer coefficient is estimated to be 8 W/m² K. Modeling the body as a 30 cm diameter, 1.7 cm long cylinder. Estimate the time of death of the person.

The following data pertains to the junction of a thermocouple wire used to measure the temperature of the gas stream. Density = 8500 kg/m³, specific heat = 325 J/kg K, thermal conductivity = 40 W/m K and the heat transfer coefficient between the junction and gas = 215 W/m² K.

If thermocouple junction can be approximated as a 1 mm diameter sphere, determine how long it will take for the thermocouple to read 99% of the initial temperature difference

A thermocouple junction in the form of a 4 mm radius sphere is to be used to measure the temperature of a gas stream. The junction is initially at 35 degrees Celsius and is placed in a gas stream at 300 degrees Celsius. The thermocouple is removed from the hot gas stream after 10 seconds and kept in still air at 25 degrees Celsius with a convective coefficient of 10 W/m² K. Find out the time constant of the thermocouple. Assume the thermos-physical properties as given below

h = 37.5 W/m² K

p = 7500 kg/m³

c = 400 J/kg K

What percentage of water an average human body can have?

Heisler charts are valid if

Amount of heat liberated or absorbed when 1A current passes is called ____________

Total seebeck effect can be found as _____________.

Which of the following element is used as a thermocouple in a nuclear reactor?

Thermocouple cannot be used to measure the temperature of the liquid.

_________________ can be used as a replacement for thermocouple lead.

Thermo couple cannot be used to measure ____________.

Peltier effect is reverse of Seebeck effect.

According to Joule’s law, if the potential difference across a conductor of resistivity r remains constant, then the heat produced in the conductor is proportional to

The term which can differentiate thermodynamics from other sciences is ____.

The energy of an isolated system

First law of thermodynamics provides

When the heat transfer into a system is more than the work transfer out of the system, then

The thermodynamic work done by the system on the surrounding is considered as ____.