<P> Mains electricity is the general - purpose alternating - current (AC) electric power supply . Mains electricity is the form of electrical power that is delivered to homes and businesses, and it is the form of electrical power that consumers use when they plug kitchen appliances, televisions and electric lamps into wall sockets . </P> <P> The two principal properties of the electric power supply, voltage and frequency, differ between regions . A voltage of (nominally) 230 V and a frequency of 50 Hz is used in Europe, most of Africa, most of Asia, much of South America and Australia . In North America, the most common combination is 120 V and a frequency of 60 Hz . Other voltages exist, and some countries may have, for example, 230 V but 60 Hz . This is a concern to travelers, since portable appliances designed for one voltage and frequency combination may not operate with, or may even be destroyed by another . The use of different and incompatible plugs and sockets in different regions and countries provides some protection from accidental use of appliances with incompatible voltage and frequency requirements . </P>

Is electricity in a house ac or dc