Which does not make use of the expansion and contraction?

Which does not make use of the expansion and contraction?

جس میں توسیع اور سکڑاؤ کا استعمال نہیں ہوتا؟
Explanation
Electric fans work using a motor, not by expansion or contraction of materials.
Devices like thermometers, electric irons, and railway tracks rely on thermal expansion and contraction.