The vast majority of power grids today operate on alternating current, and this is the type of current used by most household appliances and electrical devices in general, while cells or batteries need direct current to operate. , just like the PC. Why then does the PC need the power supply to convert current? There’s no PC running on alternating current? What is the difference? All this and much more is what we are going to explain to you in this article.
Direct current and alternating current, what is the difference?
As we mentioned earlier, the main difference between direct current and alternating current is in the way the electrons move inside the conductive material. Essentially, in direct current, electrons can only move in one direction, while in alternating current, they do so in both directions.
- Continuous current: the passage of electric current can only work in one direction, from a transmitter to a receiver or from one pole to another. It is commonly referred to by the acronym DC, which stands for direct current or direct current.
- Alternating current: the electric flow occurs alternately in both directions (hence its name), so that it goes first in one direction and then in the other direction. It is called AC from English, which means alternating current or, precisely, alternating current.
Direct current or DC
If we compare how common electricity is in the modern life we live with its existence in nature, we could say that this is an extremely rare phenomenon, as it is only generated by some animals and in natural phenomena such as lightning in thunderstorms. How then did we become so dependent on electricity?
Scientists have realized the need to artificially generate a flow of electrons in order to have energy; To do this, they first observed that a magnetic field made electrons pass from one pole to another in a natural way, so they put a wire rope or other conductive material between one pole and another to check that, well, electrons were repelled by one pole of the magnetic field and attracted to the other, but only in one direction.
Thanks to this, they developed direct current technology and the first direct current generators and batteries were born in the 19th century, attributed to the inventor Thomas Edison.
Alternating current or AC
It didn’t take long in the 19th century for another scientist, Nikola Tesla in this case, to realize that direct current was quite limited in terms of the amount of current and the distance it could be carried, he set about therefore to work to find an alternative, by proposing alternating current as a solution to the problem.
The principle is the same (with electrons being attracted to one pole of a magnetic field and repelled by the other), but instead of using a static magnetic field, Tesla used one in rotation so that when the position of the poles is changed, the direction of electron flow is also changed. The change in direction of electron flow is called frequency and is represented in Hertz (Hz) to determine the number of revolutions or cycles per second of the magnetic field. This means that if the alternating current in your house is 60 Hz, it means that there are 60 polarity changes in the magnetic change every second.
In each of the cycles, the electrons change direction and return to the point of origin, that is, there are two changes of direction for each cycle. Therefore, in an alternating current of 60 Hz, the flow of electrons changes direction 120 times per second.
What is the difference between one and the other?
The alternating current allows for example that a device can be plugged into a socket whatever the direction and without taking into account which is the negative and positive pole of the device, unlike direct current where the poles must be taken into account since ‘it only has one meaning.
As we said before, one of the disadvantages of direct current was precisely that the amount of current and the distance it could carry before losing voltage (voltage) was quite small, but this was solved with alternating current, because it multiplied into several whole numbers. both the voltage and the distance to which it could be carried.
Batteries are designed to produce direct current at a certain maximum voltage level, which already limits both the distance and the amount of current they can carry. However, alternating current can be produced in a generator and therefore a transformer can be used to increase or decrease the voltage as needed, allowing electrons to be transported over much greater distances.
AC / DC current transformers
Current transformers are used in all electrical circuits that require a certain voltage to operate. For example, when we talk about power plants, they operate at extremely high voltages so that electricity can travel long distances, but then local transformers (the ones that serve our homes) change that voltage to get us to the usual 230V. That we have. in the sockets.
The current can also be transformed from alternating to direct and vice versa using a voltage adapter or an inverter, also known as an AC / DC transformer, and it is an essential component that you have used all your time. life even if you don’t know it. , because even your cell phone charger has one, as well as the laptop charger or your PC power supply, because as we mentioned before, these devices need DC power to work.
Thus, the charger is connected to the electrical network of your house, and all the sockets it contains provide 230V of alternating current, so it is necessary to transform it into direct current for the device to work.
Why does the PC need DC power to run
In a PC, direct current is used as a form of temporary memory storage, as digital information passes through conductive paths from one logic circuit to the next. Typically, this memory functions as a two-valued storage, representing binary ones and zeros on and off (although other values such as base 3 or dense multilevel storage using stepped voltages are possible).
The conservation of the stored information requires that the voltage supplied to the logic circuits is constant, continuous and also with very precise values, which is why the power supplies also have voltage converters of 12, 5 and 3.3 volts. AC power cannot work to drive logic circuits in this way, as stored data would be lost when the ever-changing voltage drops to zero and then reverses, and that’s essentially the one and only reason a PC cannot operate today with alternating current and it must be continuous.