How fire alarm works.

This is a video of how actually a fire alarm works.

http://www.youtube.com/watch?v=jAQmGKXk2q8

This video actually shows how a fire alarm is activated.The bimetallic strip has the brass on top and the iron below. When there is heat, the brass expands faster than the iron, causing it to touch the contact point and hence the fire alarm starts to ring.

this is another video of a bimetallic strip demo.

http://www.youtube.com/watch?v=Bme1HXAPt_Y&feature=related

On the left side of the bimetallic strip, it is brass and the right side is the steel.When the lady heat both sides of the bimetallic strip equally, the bimetallic strip actually bends to one side because the brass is expanding heating up faster than the steel.

By Sy Jye

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