(a) P=IV=I^2 R. To send a lot of power along its wires the electric company needs to use either a large current or a large voltage or a combination of both. If the wires have resistance Rw then there will be power dissipated (lost) in the wires P=I^2 Rw. To minimize this loss of energy the power company chooses a large V in to make I as small as possible. In the household, however, we do not want large V because of the danger of electric shock is severe at high voltages. Thus at the point of use we want smaller voltage will allow currents to be higher
(b) Transformer
(c) Faraday's law

Physics 102 HW page