HowStuffWorks "Is it possible to generate electricity directly from heat?"

HowStuffWorks "Is it possible to generate electricity directly from heat?": "Thermocouples take advantage of an electrical effect that occurs at junctions between different metals. For example, take two iron wires and one copper wire. Twist one end of the copper wire and one end of one of the iron wires together. Do the same with the other end of the copper wire and the other iron wire. If you heat one of the twisted junctions (perhaps with a match) and attach the two free ends to a volt meter, you will be able to measure a voltage. Similarly, if you hook the two iron wires to a battery, one junction will get hot and the other will get cold."