I suggest beginning this lesson by having kids imagine and discuss what life would be like without electricity. What all they do and use everyday that would not work without electricity (whether from batteries or wall sockets). Ask: Where does electricity come from? Move on to a brief discussion of how all electricity comes from electric power plants where it is generated. Here you may show various photos of electric power plants.
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Important in this discussion is the concept that electricity does not exist in nature waiting to be gathered or tapped; it must be generated and it requires another energy source to do so: heat from burning a fuel, momentum of blowing wind or flowing water, or sunlight. Details of such things work is saved for later (Lessons C-19 and 20). Proceed to how electricity is brought from power plants to our homes, etc. via overhead power lines.
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With no more than this bear background concept of where electricity comes from, proceed to the hands-on learning of practical aspects of electrical circuity as described in the text.