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
An electric power system is a network of electrical components used to supply, transfer and use electric power. An example of an electric power system is the network that supplies a region's homes and industry with power?for sizable regions, this power system is known as the grid and can be broadly divided into the generators that supply the power, the transmission system that carries the power from the generating centres to the load centres and the distribution system that feeds the power to nearby homes and industries. Smaller power systems are also found in industry, hospitals, commercial buildings and homes. The majority of these systems rely upon three-phase AC power?the standard for large-scale power transmission and distribution across the modern world. Specialised power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail systems, ocean liners and automobiles.
Automatic garage doors
Increasingly, repair of electrical installations applies to problems with the installation, which allows the automatic opening and closing of the gate, for example, when entering the garage and so on. Such solutions are becoming more common due to its convenience and therefore need to repair this type of installation is becoming more common. First of all, the problem can occur in drives to the gates, which may not respond to user requests or for example open instead of closed. Systems control the opening and closing of gates and barriers are most commonly used in their construction, electrical components, so repair them must deal with the electrician.