# Principle of Electric current and Voltage

When we switch on a battery-powered flashlight, many small particles start to move. It is you who light up the light bulb. They are electrons that move in a certain direction in the flashlight.

The basic principle of electric current

The inside of the flashlight can be thought of as a cycle: the battery is connected to the bulb at one point by a cable. From there, another cable leads back to the battery. The electrons now travel from one point of the battery through the cable and the light bulb to the other and a current flows.

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But what makes the electrons move tirelessly through the cable? To do this, one has to take a closer look at the structure of an atom. The nucleus of the atom is formed by neutrons and positively charged particles, the protons.

The shell of the atom consists of negatively charged particles, the electrons that are floating around the nucleus. If you remove electrons from an atom, a positively charged particle remains: the cation.

But neither the electron nor the cation like this separation. Both are constantly trying to return to their original, balanced state.

There is now a point on the battery at which a shortage of electrons is generated: the positive pole. The opposite is true at the negative pole: an excess of electrons is produced. Electrons are therefore repelled at the negative pole and pushed to the positive pole.

A stream is flowing. The principle on which electrical current is based is therefore the property of the electrons to always strive for a neutral state. The current indicates how many particles move through a conductor like the cable at the same time and is measured in amperes (A).

Electricity needs voltage

So that the current flow can be maintained and does not die off as soon as the electrons reach the positive pole, electrons must be removed again and again at the positive pole. This is exactly what the battery in the flashlight does with the help of chemical reactions.

You can imagine it as if a kind of pressure is built up in the battery. This pressure arises from the difference in the charges at the negative and positive poles: the voltage. It is measured in volts (V).

Voltage can also exist without a current flowing. The current, on the other hand, cannot flow without voltage: it is only the voltage between the positive and negative pole that sets the electrons in motion.

Why does the movement of the electrons in a certain direction make the light bulb in the flashlight shine? This is because the fine wire in the bulb is an obstacle to the electrons.

They build up at the “entrance” to the wire, but they have to squeeze through. They rub against each other and produce heat. The wire in the light bulb begins to glow and there is light.