Despite all advantages of alternating current proved N. Tesla, his ideas for some time were forgotten. Americans, followers of the famous fellow countryman, completely refused transfer and consumption of a direct current only at the end of 2007.
The dispute on what will be current in the socket - to constants or variables, finally set by the ears two people – the famous American millionaire inventor Thomas Edison and then still the little-known Serbian scientist-experimenter Nikola Tesl. Won in this dispute which took place nearly 150 years ago, Edison. To tell more precisely, the victory was gained its popularity and money invested in development of the mechanisms working at energy of a direct current.
On the planet Earth today 98% of all electric power are developed by generators of alternating current. It is rather easy to make and transfer such current to long distances. At the same time current and tension can repeatedly raise and go down – to be transformed. Work is made not by(with) the tension, but current. Therefore the less its value, the is less than loss in wires.
Many users consider that in house conditions only the alternating current with tension 220B and with a frequency of 50 Hz is used. It is only fair for glow lamps, electric motors in vacuum cleaners, fridges.
In any difficult household device which is powered from the alternating current main there are knots which work at a constant tension with various values. To foresee what can be these values, it is actually impossible. Therefore all consumers in the socket have an alternating current of the same frequency and tension.
In spite of the fact that the share of development of a direct current makes only 2%, its value is rather high. The direct current is developed by galvanic cells, accumulators, thermocouples, solar batteries.
Solar batteries become very perspective direction of power in today when it is sharply asked about use of renewables.
The direct current feeds engines of locomotives on railway transport, is used in onboard network of planes and cars. On roads of the modern cities there are more and more electric vehicles and hybrid cars. For recharge of their accumulators stations which provide their needs for a direct current are under construction.
What have to be sockets
The sizes of sockets, their type, material of which they are made depend first of all on purpose of sockets, currents and tension on which they are calculated. The devices working at a constant tension have polar forks. Therefore also sockets for them have to be polar. Then even the inexperienced user will not be able to mix where "+" and "-".