Linear expansion thought experiment I have confusion with considering the outcome of the following thought experiment given the conditions:

My thought process is as follows:


*

*Brass has a higher coefficient of linear expansion. Therefore, it will have more of a tendency to contract or expand depending on a temperature change. 

*It is reasonable to suggest that compared to the system illustrated, if one rod was touching one of the electrical nodes $1$ or $2$ it would feel a higher voltage than it does now by virtue of the fact that conduction is easier when touching.

*Thus, if the metals expanded such that one of them touches $1$ or $2$, that node would be at a high (relative) voltage.

*Given the simplified scenario, it should be justifiable to only consider the linear expansion in $x$, left and right in the problem. 


Now, since brass has a higher coefficient of linear expansion, it will extend be longer than the iron after the temperature change. However, what stumped me is that, in my mind, the only expansion that would cause contact is a change in $y$, up or down. 
According to the answers provided by my lecturer, "when the strip is heated, the brass will expand more than the iron will. This means that the length on the brass side of the strip will be greater than on the iron side of the strip. This will result in the strip bending upwards, so at a high enough temperature, terminal 1 will be at the high voltage."
This seems to address my confusion, but why, intuitively speaking, would the strip curve upwards towards the short side of the strip?
 A: Imagine that the cross sections of the combined strip remain flat, and perpendicular to the interface between the two metals.  So, if the brass between adjacent cross sections extends more than the iron between the same pair of adjacent cross sections, the only way this can happen is if the composite strip bends.
A: The bimetallic strip is being subject to large forces which cause it to bend.  
When you bend a ruler the part on the "inside" of the bend is under compression because it has become shorter and so the molecules are closer together and the part on the outside of the bend has got longer and is thus under tension.  
When you heat a bimetallic strip one part expands more than the other and the forces generated are large enough to bend the strip.
A: Perhaps a more intuitive, example of this property of curves is racing. Everybody knows that it’s better to round a curve close to the inside of the curve. Why? Because the distance is shorter around the inside of a curve.
Now, for the expansion of your metal strip, if the brass component is trying to expand further than the iron component, try to think of what can happen.


*

*The brass component tears the iron component (or itself) apart as it expands.

*The iron takes the shortest path around the inside of a curve, the brass takes the long path around the outside of a curve.


Now, the first outcome could happen, but it would take much more energy, so the second outcome would be expected to occur.
Additionally, note that the linear expansion of the entire strip will be a gradient, as the expansion of each component will be effected by the expansion of the other.
