Heat and Mass Transfer
Kirchhoff's law states that

None of these
The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
The total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature
The wave length corresponding to the maximum energy is proportional to the absolute temperature

ANSWER DOWNLOAD EXAMIANS APP

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

ANSWER DOWNLOAD EXAMIANS APP

Heat and Mass Transfer
In counter flow heat exchangers

Both the fluids at exit are in their hottest state
Both the fluids at inlet are in their hottest state
One fluid is in hottest state and other in coldest state at inlet
Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state

ANSWER DOWNLOAD EXAMIANS APP