In a bimetal thermometer, what causes the bending effect when the temperature changes?

In a bimetal thermometer, the bending effect caused by temperature changes is primarily due to the difference in coefficients of linear expansion between the two metals used in the device. Each metal expands at a different rate when heated, resulting in one metal lengthening more than the other. As the temperature increases, the difference in expansion rates causes the bimetal strip to bend.

This bending motion is translated into a movement of the pointer on the thermometer scale, providing a visual indication of the temperature. The specific configuration of the bimetal strip ensures that the differential expansion effectively translates temperature changes into measurable movement.

The other aspects, such as thermal conductivity and specific heat capacity, do play roles in the overall thermal behavior of materials but do not directly cause the bending motion in the context of a bimetal thermometer. Pressure changes may also occur within the device under certain conditions but are not responsible for the bending effect associated with temperature changes in the bimetal strip.