| | Re: Physics Help Please!!!!?
Wow, lots of bad answers, no correct one.
Electricity and magnetism do not cause cancer or other diseases. That claim is simply kookery, without one iota of scientific evidence to support it. In fact, to believe that pretty much requires one ignore everything that is known about how electrical and magnetic fields interact with matter.
Voltage is a measure of how much energy a single electron has, while amperage is essentially the number of electrons you have. The danger presented by electricity is a mix of the two. High amperage at low voltage is safe, as the electrons lack the necessary energy to move through poor conductors (like your body). High voltage at low amperage is safe, as while the individual electrons have lots of energy there isn't enough of them to do damage (a balloon rubbed on your hair can have upto 100,000V). Its only when you have sufficient amperage and voltage that electricity is dangerous.
As for the OPs question, the answer is simple. The higher the voltage, the more likely you are to have electrical arching (where electricity passes between two adjacent conductors through the air - aka 'sparks'). Because consumer goods are built around quite specific expectations in regards to the voltages they will carry, it is simply unsafe to provide higher voltage levels as those products (including the wiring in your home) are not built to maintain proper insulation at higher voltages. There is also a practical limitation as well - higher voltages require better insulation to prevent arching, and insulation adds both weight and cost to products.