AC - from WIkipedia
Power in an electric circuit is the rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the direction of energy flow. The portion of power that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as active power (sometimes also called real power). The portion of power due to stored energy, which returns to the source in each cycle, is known as reactive power.
About electric industry
The electric power industry is the generation, transmission, distribution and sale of electric power to the general public. The electrical industry started with introduction of electric lighting in 1882. Throughout the 1880s and 1890s, growing economic and safety concerns lead to the regulation of the industry. Once an expensive novelty limited to the most densely populated areas, reliable and economical electric power has become a requirement for normal operation of all elements of developed economies.
By the middle of the 20th century, electric power was seen as a "natural monopoly", only efficient if a restricted number of organizations participated in the market; in some areas, vertically-integrated companies provides all stages from generation to retail, and only governmental supervision regulated the rate of return and cost structure.
Since the 1990s, many regions have opened up the generation and distribution of electric power to provide a more competitive electricity market. While such markets can be abusively manipulated with consequent adverse price and reliability impact to consumers, generally competitive production of electrical energy leads to worthwhile improvements in efficiency. However, transmission and distribution are harder problems since returns on investment are not as easy to find.
Is always in the case of electrical failure we call for help?
The virtual network is a source of information of all kinds, and this is primarily due to the fact that anyone who has access to the Internet, you can actually write anything there. When it comes to electrical services, this issue looks the same. The Internet is full of advice relating to self-repair minor faults. If they do not come from a known source, however, we should not make major repairs on their own. Websites specific electricians also contain different advice, but here they concern primarily the need to call an electrician. It may turn out that insufficiently tightened the fuse will make that we will be deprived of light, and for such a trifle is not worth it to call professional help.