Figure shows a system that is proposed to power a radio from the heat of a portable lantern. There are eight "wings" on a shield around the lantern flame. Each wing has type J thermocouples facing the flame, with the cold junctions on the outer edge of the wings. A radio in the base requires a minimum of 5.0 V at 50 mA to operate. The following assumptions are made:
(1) Each thermocouple segment has a resistance of , and
(2) the flame heat at the thermocouple junction is at least and nominal room temperature is .
a. Determine how many thermocouples are required and how they are distributed on the wings. Be sure to consider the internal resistance of the thermocouples.
b. What is the maximum power that can be delivered into any load at and at ?
c. On a cold winter night, the ambient temperature can drop to . If the hot junctions are still at , what effect does this have on the voltage applied to the radio?
