Eduard-Job-Foundation for Thermo- and Matterdynamics

Experiment 3.3: Expansion of a Wire Caused by Electric Current

Expansion_Wire.jpg

Procedure:
First, the current is slowly increased. Then, the current is decreased again.

Observation:
The weight sinks down slowly with increasing current. At higher current, the wire also begins to glow. If the current is decreased the weight moves upwards again. ??

Explanation:
Entropy is generated by the electric current. As main effect of the increase in entropy the wire becomes warmer and finally begins to glow. But the increasing entropy also causes a side effect: The wire lengthens noticeably. If the electric current is decreased again, also the entropy generated in the wire decreases; the wire gradually cools down and shrinks again.

Video (mpg4, 1:04)