Final answer:
Calorimetry directly measures total energy expenditure by tracking the heat generated by a person, related to their metabolic rate. Meanwhile, a calorimeter is a tool used to measure the amount of heat (heat) involved in a chemical change or reaction.
Step-by-step explanation:
Direct calorimetry is a method used to measure an individual's total energy expenditure by tracking the heat they produce. This is achieved in a specialized chamber where a person can live and work, allowing their total heat output to be monitored over time. The Atwater calorimeter, a piece of historical equipment, once allowed for such measurements, directly correlating a person's energy expenditure to their net energy intake.
The working principle of the calorimeter is to flow an electric current through a coil of conducting wire that is inserted into distilled water. When moving in a conducting wire (due to potential differences) charge carriers collide with metal atoms and lose energy.
Your question is incomplete. The meaning of your question is:
Direct calorimetry measures a person's oxygen consumption and carbon dioxide production. So what is the function of a calorimeter?