Sunday, 17 August 2014

Think 6

Group Answer
Metal B is a better thermal conductor than metal A. Thus metal B expands faster than metal A since its molecules are able to gain kinetic energy faster and thus it will expand faster. With both metals sticking together, and metal B expanding faster, the whole bimetallic strip bends towards metal A.
When the whole bimetallic strip is cooled (water poured), the molecules of both metals lose kinetic energy. Thus as metal B is a better thermal conductor its molecules loses kinetic energy faster and thus in contracts faster. Since they are stciked together and metal B contracts faster, the whole bimetallic strip bends back to its original straight shape, where both metals have a same length.
Individual Answer
Macro
When the whole metallic strip is heated, as metal B is a better thermal conductor then metal A, metal B would have a greater expansivity than metal A. This causes metal B to gain more thermal energy than metal A and thus metal B can expand more. Having to expand more and also because they are sticking together, the whole bimetallic strip will bend towards the direction of metal A. 
When water is poured on the bimetallic strip, as metal B is a better thermal conductor, it will also contract faster due to the lost of thermal energy and therefore the whole bimetallic strip will bend towards metal B
Micro
Metal B is a better thermal conductor than metal A. Thus the molecules of metal B will gain more kinetic energy and the molecules in metal B has more collisions than the molecules in metal A. This causes the whole bimetallic strip to bend towards metal A, since metal B is expanding at a higher rate and the two metal strips are sticked together.
When the water is poured on the bimetallic strip, molecules of metal B loses kinetic energy faster than the molecules in metal A since metal B is a better thermal conductor. Thus the whole bimetallic strip will quickly shrink back to its original straight position. 

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