Homework Help: Physical Science

Posted by mysterychicken on Monday, May 11, 2009 at 10:41am.

Need help with these questions-

1.What causes an electric current in a wire?
A.Electric feilds cause atoms to move in the wire
B.Electrons flow because of electrical attraction and repulsion
C.Electrons move because of heat
D.Electrons build up in the wire and create a charge
B?

2.How does an insulator stop the flow of an electrical current?
A.Insulators have too many electrons
B.Insulators have a positive charge so they absorb electrons
C.Electrons in an insulator don't move readily
D.Insulators convert electric energy into other forms of energy
???

Thanks!
-MC

Physical Science - Count Iblis, Monday, May 11, 2009 at 10:59am
1:

B) looks like the best answer.

A better answer would be to take A) and replace "atoms" by "electrons".

2: C is the best answer. Electrons are in "bands" analogous to electrons in atoms in shells. In insulators the bands are fully occupied, in conductors there are bands that are not fully occupied.

If a band is not fully occupied, you can shift the momentum of each electron and create a current that way. If a band is fully occupied nothing can change.
Physical Science - mysterychicken, Monday, May 11, 2009 at 11:12am
thanks!
-MC

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