Thermometer and electric fan: what they have in common

1. Step 1. Thermometer — uses — Thermal expansion. A liquid expands when heated.
2. Step 2. Thermal expansion — is used in — Bimetallic strip. Metals expand differently.
3. Step 3. Bimetallic strip — is part of — Hair dryer. Overheating protection: when hot, a bimetallic strip bends and breaks the circuit.
4. Step 4. Hair dryer — has part — Impeller. An impeller on the motor shaft pushes air through the heater.
5. Step 5. Impeller — is part of — Electric fan. A fan's blades are an impeller that pushes the air.

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