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Heat causes some 1_______ to expand more than others. For example, copper expands more than 2_______. This effect is used in the bimetal strip, which consists of two dissimilar strips of metal 3_______ together. The strips are usually made of brass (an alloy of copper and zinc) and invar, a ferrous alloy which expands very little when heated.
An increase in 4_______ causes the brass to expand more than the invar. This expansion causes the bimetal strip to bend, and consequently a switch or a valve is activated.
metals
iron
welded
temperature