When a bimetallic strip is heated. Then it bends towards which element. ie element having
high value of temperature cofficient of linear expansion or low value of that. Or is there
something else the truth.. i dont know how 2 attempt such question.

binayakafle,

bi metalic strips are used in toasters, kettles and so forth. The principle of a bimetalic strip is a combination of two metals which have different thermal coefficients of expansions (delta L = alpha * Lo * delta T) alpha being the expansion coefficient. Higher alpha means larger delta L for the same Lo and delta T. The bending will occur if the endpoints are attached in some fashion, and it will bend to compensate for the length of the higher coefficient of expansion which will be situated on the outside of the curve as this side has the greater length.

If you boil some water in a regular kettle with the lid closed it will stop boiling. With the lid it will not stop boiling which shows that the temparature of activation of the bimetallic strip is set at slightly above the boiling point of water. (1200m amsl or there abouts)