# Electric current

We have seen that electrons move easily in conductive bodies. The displacement of these electric charges is called electric current.

Electric current is responsible for the operation of electrical appliances; These only work when the current flows through them.

Current through a device is only possible if it belongs to a closed circuit.

A circuit consisting of lamp, battery and wires, when properly connected, form a closed circuit. When we turn on the electrical appliances in our house and they work, we can ensure that they are part of a closed circuit when it passes electric current through its wires.

## Understanding the electric current

Before we define electric current, let's imagine the following situation: You are in an urban or subway train station where the passenger goes through roulette wheels to gain access to the trains. Its purpose there is to evaluate the amount of people passing by the minute.

Getting this information is simple: just count how many people pass in a minute. For example, if you counted 100 people, you would answer that 100 people pass per minute. To achieve a better average, you can count on longer. Let's say you counted 900 people in 10 minutes.

So your average will now be 900/10 = 90 people per minute.

Then someone asks you to rate the average mass of people passing the roulette wheel per minute. You accept the challenge.

If the average mass of people in Brazil is 70 Kg (we can see this when reading building elevator signs, which always consider the mass of a person equal to 70 kg. These warning signs attached to the cabs state: “Maximum capacity: 10 700 kg ”).

Average mass

This idea is similar to that used to define the intensity of electric current (i). The charge of an electron is known to be equal to 1,6.10- 19 Ç .

If you could count the amount of electrons (n) which crosses a flat region of a wire in 1 second could state that the intensity of the electric current is:

If it counted for a period any, and representing the electron charge (1.6.10- 19 C) by the letter e, could say:

This is the mathematical expression associated with the intensity of the electric current.

The unit of electric current intensity is the Coulomb per second, called amp (A). Electric current can be continuous or altered.

In direct current observed in the batteries, the flow of electrons always occurs in one direction only.

In alternating current, the electrons alternate the direction of their movement, oscillating this way and that. It is this type of current that is established when we connect the devices to our home network. The reason for the alternating current is related to how electricity is produced and distributed to our homes.