physics tutor-how do thermostats work

It is a device for maintaining steady temperature in various electrical appliances like airconditioners, refrigeretors, room heaters, electric press, ovens, etc. It consists of a bi-metallic strip
having invar and brass. since these metal have their own temperature co-efficient of expansions, hence expand at
different rate. Brass expands more than that of invar so it bend towards invar on heating.This bimetallic strip
is fitted with a flat steel spring which can be tightened or loosed by the control knob. these bimetallic strips
are connected with contact points.A heating element is connected with the bimaetallic strip as shown.

When current is passed through the given heating element, it gets heated. Now bimetallic strip starts bending toward invar side thereby disconnecting the current path. as a reasult heating
element will cooled down. On cooling bimetal moves in the reverse direction and again the electric current is restored. Thus a constant current is maintained.

video link for temperature coefficient of thermal expansion is
https://www.youtube.com/watch?v=-JDR1LNQmjM

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Видео physics tutor-how do thermostats work канала educlub 4u