To show the unequal or differential expansion of two different metals in a bimetallic strips. Comprising two strips, each of different metal but if same size, riveted together end to end and fitted on an insulated handle. On heating, the compound strip bends into curvature with metal having more coefficient of expansion on concave side and other one on convex side. Returns back to its original shape on cooling. The thickness of the two metal strips selectable carefully so as to obtain sufficient curving on applying little heat. Comprising a length of bimetal strip 150 × 20mm mounted in a wooden handle. The strip is only 1.5mm thick so that very little heat is required to produce considerable bending. Length overall 270mm approx. 1060260/1 Brass and Invar; 1.5mm thick with strip size 150×20 length × width) 1060260/2 Copper and Iron; size about 200×25mm (length × width) 1060260/3 Brass and Steel; size about 200×25mm (length × width) 1060260/4 Brass and Iron; size about 300×30mm (length × width), with new improved design