The electric currents generated by cells and batteries are of the continuous type, that is, they travel along the conductor wire always in the same direction. These electrical voltage sources always have two distinct poles, that is, a positive pole and a negative pole. The direction of the electric current, in this circuit, is always the one indicated (clockwise).
The electrical current we receive in our homes is of the alternating type . This kind of current undergoes constant reversal of direction. In the Brazilian electric energy transmission system, 120 inversions occur every second, that is, the electric current, every second, runs through the conductor 60 times in one direction and 60 times in the opposite direction.
Therefore, we say that the electric current in Brazil has a frequency of 60 Hz or 60 cycles per second. Some countries, such as Japan, use the 50 Hz frequency. Due to these several inversions of direction, which occur every second in alternating currents, we cannot identify, for example, in a socket, which of the poles is positive or negative.
physics and technology
The alternator used in vehicles is responsible for generating electric current, which feeds the car’s electrical circuits, as well as recharges the battery that works when the car is not working. It is good to remember that alternator is different from generator. Although they are very similar, they have a basic difference: alternators generate alternating currents, while generators (dynamos) generate direct current.