I have last question. When I have power supply (battery) it supplies electricity to the electrical circuit. So the electrons are "moving" through the circuit from the "-" to "+" (in the real world i suppose). So after the electron passes through the circuit it is coupled with some proton on the + "end" of the battery? So finally at the end there are no electrons attracted by protons in the battery?

And where are electrons going when I use some transformer, wall wart or something.

Thank you!

Power/energy first, then equilibrium? This is not my level of expertise but I know that there are people here that can answer that question.

 

One note though, I would say controlling the voltage drops and the current is the resistors primary role.

Excellent point.

When I have power supply (battery) it supplies electricity to the electrical circuit. * * * So after the electron passes through the circuit it is coupled with some proton on the + "end" of the battery? So finally at the end there are no electrons attracted by protons in the battery?

I believe so. There is an abundance of electrons (negatively charged) at the negative end of the battery and an absence of electrons at the positive end. So, yes, once they reach and mate to a proton the electron is happy at home and it doesn't move anymore.

As far as the wall wart - AC (Alternating Current) (to quote #12 - electrons wiggle back and forth) those electrons passing through a coil of wire wrapped around an iron core generates a magnetic field. Every time the AC changes direction the magnetic field has to change too. It's the changing magnetic field that makes a transformer transform the voltage. When the magnetic field collapses it induces electrons in the wire to move. Thus, the term "Inductance". Depending on how many windings are on the primary (first) side and how many on the secondary. Here are some made up numbers to help you understand: (actual numbers are way higher): Suppose you have a primary with 100 turns of copper wire and a secondary with only 10 turns of copper wire. That's a 10 to 1 (or 10:1) transformer. Meaning if you put 120 volts AC on the primary it will transform (or induce) a voltage of 12 volts on the secondary. Transformers can work the other way too. Such as a microwave transformer that changes 120 VAC (in America, or 240 VAC in many European countries) to 1,000 volts. In your micorwave there is a hgh voltage diode and a capacitor. The way they're configured, when the AC goes one way it charges the capacitor. When it goes the other way the voltage is added to the stored charge in the cap. The resulting DC voltage is 2,000 volts. So yes, a transformer can boost voltage or drop it. It can also isolate a circuit from the main power line. Such an isolation transformer may be a 1:1 ratio, not really changing the voltage, just isolating it from the main lines.

Be advised, you can't just take a 10:1 transformer and turn it around and stuff 120 volts in the secondary and expect to get 1200 out of the primary. The wire coil that makes up the secondary may not be able to handle that much voltage going into it and the primary may not be able to handle the 1200 volts coming out of it. Transformers are fussy beasts.

One last thing about transformers, they're not perfect devices. There ARE losses. So if you put 100 watts of energy into a transformer you're not going to get 100 watts out. Watts is amps times voltage. High voltage low amps, high amps low voltage. In theory they're supposed to balance out. But in the real world they don't.

 

Sorry, I don't get the part with p.E (shortcut??) sorry for my english or electronic abbreviations.

And please, where do you get 330 Ohm or 150 Ohm?

Sorry for my stupidity, I need to understand these basics. Can you please show me how to calculate the current in the circuit and required resistor for the LED?

Thank you

Calculate? Have you considered measuring the current and the voltage across the LED? Use different resistors and see how it changes these things.
If you don't have a data sheet for the LED you can't make calculations. What is the voltage across the LED at what current? A data sheet has a chart telling you this. You are right. Without that you can't make a calculation. The alternative is to actually measure it at different currents and create your own graph.
(edited to add ...)
Search this forum for "LED exercise".