How do thermostats for for ceramic heat emmiters in terrariums work?

Question

How do thermostats for for ceramic heat emmiters in terrariums work?

Answer 1

They're usually bimetallic thermostats.  Two strips of different metals welded together.  They expand and contract at different rates for temperature changes.  One end is held fast, the other end has an electrical contact on it.

When the temperature changes, the different expansion rates causes the metal strip to bend.  When it gets colder it bends in the direction that makes the electrical contact touch another, fixed, contact, making an electrical connection, turning the heater on.