A bimetal thermometer consists of which of the following?

A bimetal thermometer operates on the principle of thermal expansion and consists of two dissimilar metals that are welded together. When the temperature changes, the two metals expand at different rates due to their differing thermal expansion coefficients. This difference in expansion causes the bimetal strip to bend, which then moves a pointer on a calibrated scale to indicate the temperature.

The use of two different metals is key to enabling accurate temperature measurement. Each metal’s unique response to heat ensures that the thermometer can reliably convert temperature changes into mechanical movement, which is readable on the scale. This mechanism makes bimetal thermometers effective for a variety of applications where precision in temperature reading is important.

The other options do not accurately describe the structure or functioning of a bimetal thermometer. For instance, a filament (as mentioned in one of the choices) does not pertain to the bimetal thermometer's design or operation, while the generation of voltage by two metals when heated refers to thermocouples, not bimetal thermometers. Furthermore, two connected copper wires pertain to other types of sensors, not to the functioning principles of a bimetal thermometer, highlighting why they don’t align with the characteristics of the thermometer in question.