In this lesson students will learn about thermoelectric devices
(TED) and plot Voltage Vs Temperature graphs for the devices. 
Thermoelectric devices work two ways.  When a voltage is
applied to them one side gets hot and the other side cools. 
Some travel coolers work this way.  The other mode works the
opposite way. When the device is subjected to a temperature
difference, it produces a voltage.  It is like a solar cell
that responds to heat.