# Electric current This system has an electrical potential difference (ddp) or electrical voltage.

Electric current flowing through resistors can transform electrical energy into thermal energy (heat), a phenomenon known as the Joule Effect .

The resistance of a conductor wire facilitates or hinders the passage of electric current, being calculated using the formula of First Ohm's Law ( R = U / I ).

Electronic devices, batteries, have the negative pole and the positive pole. This explains the potential difference (ddp) present in each of their circuits.

Note that the sense of the electric current is characterized in two ways. One of them is the " real electric current ", that is, the one that has the sense of electron movement.

The other way is the " conventional electric current ", whose meaning is contrary to the movement of electrons and is marked by the movement of positive electric charges.

In the International System of Units (SI), the intensity of the electric current is measured in Amp (A), the resistance in Ohm (Ω) and the electric voltage (ddp) is measured in Volts (V).

Read also Joule Effect and Kirchhoff Laws.

## Electrical Conductors

Electric conductors are materials that allow the movement of electrons, ie the passage of electric current. A material is considered an electrical conductor depending on the potential difference to which it is subjected.

The best electrical conductors are metals, on the other hand, materials that make it difficult to Electron movement are called insulators. Examples are wood, plastic and paper.

There are three types of drivers :

• Solids - characterized by the movement of free electrons;
• Liquids - movement of positive and negative charges;
• Gaseous - cation and anion movement.

## Electric Current Types

• Direct Current (DC) : has constant sense and intensity, ie has continuous potential difference (ddp) generated by batteries and batteries.
• Alternating Current (AC) : has varying meaning and intensity, ie has potential difference (ddp) is alternated, generated by the plants.

## Electric Voltage

Electrical voltage, also called potential difference (ddp), characterizes the two-point electrical potential differential in a conductor. It is, therefore, the force arising from the movement of electrons in a given circuit.

In the International (SI) system, the electrical voltage is measured in Volts (V). To calculate the electrical voltage of an electrical circuit, we use the expression: