Thermocouples can also generate heat from electricity, and even cold from electricity, acting as a refrigerator. If two different wires are connected at both ends, and some voltage source makes current flow through the loop, one junction will get hot and the other junction will become cold. The electrons at the hot junction are gaining kinetic energy as they cross the junction. This is why they make the metal hot. The electrons at the cold junction are losing kinetic energy as they cross the junction. This is why they make the junction cold.