In India, we use 220V as the amplitude of the sinusoidal ac current in our houses. The reasons for choosing this particularly odd value are historical. But my question is - what? What is the reason for this convention?
I could suggest several considerations. First P=IE, that is Power equals the electrical current (I in Amperes) times the voltage (E in volts). Current is like the flow of water in a pipe and voltage is like the pressure causing the water to flow. If you use the water to drive a hydraulic piston (say to hoist an automobile for repair) you can use either a small piston and high pressure or a larger piston and lower pressure. Which is more cost effective?
In the United States, electric power is delivered to neighborhoods using three wires (three phases) strung along telephone (power) poles. Only two of the wires are led to a single residence but the neighborhood must use all three wires to balance load on the wires. Within a house electricity passes from only one wire (phase) to ground or earth to light a lightbulb which uses 110 volts. The clothes dryer that needs far more power is connected between two of the supply wires (two phase) and to ground to supply 220 volts. A machine shop might connect a very large motor to all three supply wires to obtain even more power at 440 volts.
Six volts or even 12 volts DC in an automobile circuit can be touched with little danger. It is less dangerous to accidentally touch a 110 volt AC wire than a 220 volt source and 440 volts is most dangerous.
Therefore, the selection of voltage depends in part on safety and then on the size of the job to be tackled and also economic factors. The higher the required current, the larger the required wires using expensive copper. Increasing the voltage reduces the needed current and reduces the needed copper to do a given job. The higher the required voltage, the more expensive the required electrical insulation will be. Engineers must determine the best trade off of many factors.