Compound Bar Bonded Bimetallic Strip, 150 × 12.5 mm, Plain

Description

The Compound Bar Bonded Bimetallic Strip, 150 × 12.5 mm, Plain, also known as a bimetallic strip, compound metal bar or thermal expansion demonstration bar, is designed to demonstrate how different metals expand at different rates when heated. Manufactured by IEC (Industrial Equipment & Control Pty Ltd), this educational physics apparatus consists of two different metals permanently bonded together. The metals have different coefficients of linear thermal expansion, allowing their behaviour to be observed during heating experiments. The compound bar measures 150 mm in length and 12.5 mm in width, providing a compact demonstration instrument for studying heat and thermal expansion. Its plain construction does not include an attached handle.

The two bonded metals feature contrasting copper-coloured and silver-coloured surfaces, allowing students to recognise that the bar contains two different materials. This visual distinction helps explain the structure and operating principle of a bimetallic strip. Unlike traditional compound bars assembled using rivets, the modern bonded construction joins the two metal layers face to face. This permanent bond allows the metals to act together while responding differently to changes in temperature. When the compound bar is heated, each metal attempts to expand according to its individual thermal expansion coefficient. Because the layers are bonded, they cannot expand independently, causing the strip to bend.

The metal with the higher coefficient of thermal expansion expands more and forms the outside, or convex surface, of the bend. The metal with the lower expansion coefficient forms the inside of the curve. This visible movement provides a practical demonstration of differential thermal expansion, helping students understand why materials respond differently when exposed to the same temperature change. As the strip cools, it generally moves back towards its original shape, provided it has not been overheated or permanently deformed. Students can observe the relationship between heating, cooling and changes in curvature.

The apparatus is particularly useful for explaining how bimetallic thermostats and temperature-sensitive switches operate. These devices use the bending movement of bonded metals to respond mechanically to temperature changes. The plain, handle-free design requires suitable laboratory tongs or a secure heat-resistant clamp during heating experiments. Users should avoid holding the metal directly when applying heat. The bar supports physics practical lessons, thermal expansion investigations and classroom demonstrations involving heat transfer, temperature changes and the mechanical behaviour of metals.

Safety Precautions: Use appropriate heat-resistant holding equipment and conduct flame-based experiments under supervision. Do not touch the heated bar directly. Keep combustible materials away from the heat source and allow the metal to cool before handling or storage. Each unit is supplied as one IEC Plain Bonded Compound Bar measuring 150 × 12.5 mm. A handle is not included, and heating equipment or holding accessories must be provided separately.

LabChoice Australia supplies compound bars, bimetallic strips and educational thermal physics apparatus for secondary schools, universities and science teaching laboratories across Australia.