Final answer:
Residential voltage in the U.S. is typically 120 volts RMS and in Europe, it is 220 volts RMS. Appliances have different power ratings based on their function, and power companies use high-voltage transmission with transformers to efficiently deliver electricity to homes.
Step-by-step explanation:
Voltage for a residential dwelling will typically be found by a home inspector to be 120 volts in the United States and 220 volts in Europe. These voltages represent the root mean square (RMS) values, which are the equivalent to the DC values for a simple resistive circuit.
While the peak voltage values are higher (170 V in the US and 311 V in Europe), the RMS value is quoted because it is standard practice, considering RMS values correlate to the actual power usage.
For example, a typical circuit in the U.S. is protected by a 10-ampere circuit breaker; considering the household voltage is 120 V, this corresponds to a power capacity of 1.2 kW for that circuit. Appliances have various power ratings depending on their energy requirements; a toaster will consume much more power than a digital clock because it is designed to generate heat, which requires more electrical energy.
Electrical companies deliver power at high voltages and use transformers to step down the voltage for residential use. This high-voltage transmission is more efficient despite some energy loss through heating of the wires, because it allows for transporting power over long distances with smaller current, hence reducing energy loss due to resistance in the wires.