ICSE Class 8 Answered

(1) A bimetallic strip is used to convert a temperature change into mechanical displacement. The strip consists of two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases steel and brass. The strips are joined together throughout their length. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. The sideways displacement of the strip is much larger than the small lengthways expansion in either of the two metals. This effect is used in a range of mechanical and electrical devices.

(2) In order to make tight fitting of metallic rim on wooden wheel, first the metallic rim is heated and is allowed to expand. Then the rim is fitted on wooden wheel. After cooling the rim contracts it size, thus making tight fitting on wooden wheel.