Answers

2014-05-28T12:12:27+05:30
Make an artifical eco system (field)
make irrigation system
make house security system
how to obtain groundwater 
how to generate electricity
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2014-05-28T12:15:36+05:30

the 5 easy working models are :-
1) to make an electric circuit
2)to show that fire needs oxygen to burn
3)pin hole camera
4)kaleidoscope
5)volcano
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