How does the consumer set the current strength for the source?

Question

Electronics

Sorry for the crooked question, if that.

Answer 1

In the general case - through Ohm's law, with which you are not familiar.

Answer 2

I can advise you to go to college. There is such a subject "Theoretical foundations of electrical engineering" (TOE). There are different versions of the names, but the essence is the same.
They are studied from simple circuits (linear) and simple calculations, to complex circuits. And it ends with non-linear elements, like diodes, transistors (although this is already like electronics? - but still the same Ohm's law works). And the icing on the cake is alternating current, pulsed, transients, capacitors-inductors ... and calculations in complex numbers (yes, mathematics is needed here, and physics too).
PS The I-V curve of the LEDs has already been given to you, it remains to study such concepts as a voltage source, a current source, understand the principles and the difference, and understand how real sources differ from ideal ones. And also to study ways of solving problems with non-linear IV characteristics. The easiest way is graphically, because the I-V curves of (light-emitting diodes) diodes are highly non-linear, and are rarely simply described by any equations. I suspect that if all this is explained here, the answer will stretch for a hundred pages, and still it will not be possible to explain it better than in the textbook.

Answer 3

if you are talking about the CC mode (constant current - stable current value) of the laboratory power supply, then by measuring the current in the output circuit, the error signal is transmitted to the voltage regulator (usually PWM).
those. the output voltage is set to such a level as to provide the required current in the circuit.

Answer 4

If Ohm's law does not give in, then you can always imagine an analogy with water.
Voltage - the height of the water column (or water pressure)
Current - water flow in liters / sec, how much water will flow through a section in 1 second
Resistance - how much the section slows down water. This may be due to the cross section of the pipe, its length, or its condition (rusty, clogged, etc.)
There is a voltage source (or rather, EMF ) - a pump that creates a constant pressure drop (in electricity - a battery, or a power supply that holds voltage)
Or a current source - a pump that keeps a constant flow of water, regardless of resistance
We connect a load that has resistance - the dependence of water flow on pressure (in electronics - current on voltage). This is called the volt-ampere characteristic.
If we return to the first question, then the device passes as much water (current) through itself as it can at all . There will be a limitation either of the current source (the pump cannot give so much water per second) or the device itself (its resistance), or the connecting wires (pipes, hoses).
easyelecronics had a series of articles on "sewer electronics" to help you get the hang of it .