Science Buddies: "Ask an Expert"

My daughter has this project due and I dont have a clue where to begin to help her. She has to build an alarm with either sound or a light that comes on when the circuit has been broken. I've been outta school for a while but I dont remember learning about this when I was there.
Anyone have any ideas please??
Thank you.

Hi TexasStyle4u!

You can try the wikipedia entry at:

http://en.wikipedia.org/wiki/Burglar_alarm

The wikipedia article has a good discussion of the issues.

What skills and equipment do you have? Are the experimenter isles of Radio Shack places you've never visited?

Turning something on when another circuit is broken requires a logic inversion. A relay, a transistor switch, an integrated circuit can all be used but this maybe more than what you are actually being asked to do.

Figure out if you can simplify the problem by using a switch that is open when depressed and closed when released. This would allow you to use a much simpler circuit that has a battery and the switch and a light all in series.

http://www.1728.com/project2.htm has a burglar alarm diagram.

What parts are available at school? Have you talked with the teacher for recommendations on where to get parts to use?[/url]