Final answer:
The thick callus on the bottom of a person's foot acts as an insulator and reduces the amount of heat transferred from red hot coals through conduction, preventing burns.
Step-by-step explanation:
One of the main reasons a person can walk barefoot on red hot coals of wood without burning their feet is due to conduction. Conduction is the transfer of heat through direct contact between objects. When a person walks on the coals, the heat is transferred from the coals to their feet through conduction, but the rate of heat transfer is limited by the 3.00-mm-thick callus on the bottom of their foot. The callus acts as an insulator, reducing the amount of heat that reaches the skin and preventing burns.