Current is defined as an organized movement of electrons through the electrical conductor or space. Each electron carries a certain charge. The movement is caused by a potential difference. It seems complicated but, it’s not. Let’s suppose that we have a waterfall where water falls from a higher level (higher potential) to a lower level (lower potential). The movement of water is caused by a height difference (potential difference) and it continues until the water from the lower level equals the water from the higher level. The same goes for electron movement, it last until the balance is attained. However, unlike water, in this case, the potential difference is not the height difference, but the voltage. Current flows from a higher electrical potential to a lower one. The unit of current is the ampere [A].

The mentioned voltage is responsible for the force of current flow. The voltage is expressed in volts [V]. The combination of voltage and current gives us energy. We can not forget about resistance which disrupts the flow of current. The unit of current is the Ohm [Ω].

AC stands for alternating current. We have DC and AC electricity. Direct current (DC) refers to systems in which the movement of electrons goes in one direction and is unchangeable over time, which results in constant current and voltage. In alternating current, both voltage and current change their direction and magnitude with time. These changes are characterised by a sinusoid, which is shown in the figure above. The sinusoid is described by the amplitude – the largest value of a quantity varying periodically and wave cycle – time between occurrences of the same phase of the oscillation.

AC current is created in power plants by generators and then it is supplied to our houses and flats. As we can see in the diagram, as the magnitude is changing with time, it takes positive and negatives values periodically. That’s why we need to introduce the concept of effective values. It is a statical measure of a periodically varying signal.

The most important parameters of alternating current are voltage and frequency. Voltage has been described above, but what is frequency? It is a number of wave cycles that occur per second. Both voltage and frequency values are described by effective parameters.

The parameters of the current in sockets:

- Voltage 120 [V]
- Frequency 60 [Hz]

AC compared to DC can be easily converted to and from high voltages by using transformers. This provides AC with an advantage well above DC in the field of power distribution and contributes to lower energy losses.