If an iron rod, inside two coils, incurs current going through the coils in the same direction, then the rod will increase in length and then it will begin to reduce in length. This is due to the magnetostrictive properties of the iron. When the currents oppose each other, so as to cancel, then the thermal properties only can be studied. That is, without the influence of magnetostriction. The iron rod would increase in length due to the heat input. But will it get to a certain length, then stop? That is, as the heat input continues to rise. As the heat input continues to rise, I presume it won't reduce in length? Thank you.