Chapter 4: Q21DQ (page 841)
Ordinary household electric lines in North America usually operate at 120 V . Why is this a desirable voltage, rather than a value considerably larger or smaller? On the other hand, automobiles usually have 12 V electrical systems. Why is this a desirable voltage?
Short Answer
The households have long wires so keep the power the voltage must be kept high.But in the car the wires are small so the resistance is small so there is no need for high voltage.