Warning: We believe in experimenting and learning about physics at every opportunity, BUT playing with electricity can be EXTREMELY DANGEROUS! Do not try to build home made circuits without someone who knows if what you are doing is safe. Normal electrical outlets are dangerous. Treat electricity with respect in your everyday life. You will encounter electricity every day for the rest of your life and to make sure you are able to make wise decisions we have included an entire chapter on electrical safety. Please read it - not only will it make you safer but it will show the applications of many of the ideas you will learn in this chapter.