Heat and Mass Transfer
Depending on the radiating properties, a body will be black when(Where a = absorptivity, p = reflectivity, X = transmissivity.)

P= 1, T = 0 and a = 0
P = 0, x = 0 and a = 1
X = 0, a + p = 0
P = 0, x = 1 and a = 0

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Heat and Mass Transfer
The time constant of a thermocouple is

The time taken to attain 50% of the value of initial temperature difference
The time taken to attain 63.2% of the value of initial temperature difference
The time taken to attain the final temperature to be measured
Determined by the time taken to reach 100°C from 0°C

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