What is a bimetal?

What is a bimetal?

• A. A device consisting of two wires of dissimilar metals joined at one end, generating a small voltage when heated.
• B. A device consisting of two identical metals.
• C. An insulating material used in circuits.
• D. A device that stores electrical energy.

Answer: (A)

A bimetal is made from two metals with different rates of expansion bonded together. When temperature changes, each metal expands or contracts by a different amount, so the strip bends. That bending can push or release contacts or actuate a valve, giving a simple, passive way to sense temperature and control or limit operation in gas appliances. The description that two dissimilar metals joined at one end produce a small voltage when heated refers to a thermocouple, which relies on the thermoelectric effect to generate electricity rather than bending. The other options don’t fit because identical metals won’t bend like a bimetal, an insulating material isn’t metal, and a device that stores energy isn’t a bimetal. In short, a bimetal controls temperature or safety by mechanical bending, not by generating voltage.

A bimetal is made from two metals with different rates of expansion bonded together. When temperature changes, each metal expands or contracts by a different amount, so the strip bends. That bending can push or release contacts or actuate a valve, giving a simple, passive way to sense temperature and control or limit operation in gas appliances.

The description that two dissimilar metals joined at one end produce a small voltage when heated refers to a thermocouple, which relies on the thermoelectric effect to generate electricity rather than bending. The other options don’t fit because identical metals won’t bend like a bimetal, an insulating material isn’t metal, and a device that stores energy isn’t a bimetal.

In short, a bimetal controls temperature or safety by mechanical bending, not by generating voltage.