So I’m a beginner in electronics. I’m trying to teach myself because I never had a teacher to explain anything. One of my things is that it’s hard for me to understand something without fully understanding the fundamental basics, which has kept me from progressing in my self-study.
I can’t understand why electrical current shares its power across its loads in a circuit (series, obvs).
For example, a 12 volt battery is connected to a lamp. That lamp gets 12 volts of electricity running through its filaments (or LEDs or whatever). If there were 2 identical lamps in series, then that 12 volts would be split up between each lamp, which would result in them each getting only 6 volts.
But why? The electrons don’t know what the whole circuit looks like, they don’t know or care about how many loads there are. When the actual electron flow hits upon the first load in the circuit, why shouldn’t they act the same as if there is one load? Why would they behave as if there were more loads? At that time, when the electrons are meeting that first load, what makes them go, “only going to be half as bright, buddy”?
My dad tried to help by showing the equation of amps and volts and current, but that doesn’t answer my question at all. It only says it does do that, but it doesn’t tell me WHY.
In: Technology
Ignore the electrons. The electromagnetic field does all this at the speed of light, the electrons are irrelevant. They might take three hours to round the DC, they have absolutely no clue what is happening further down.
You have two light bulbs, a battery, and a switch. The switch is open. You close the switch and… no electrons move. Why? Inductance. When the switch closes, the electric field rockets around the circuit at the speed of light telling electrons to get moving. It’s comparable to the gravitational field telling mass to roll downhill. The electric field will just make a constant slope all the way down the circuit, or equal voltage drop everywhere. From 12V at the positive terminal, to 0V at the negative. Like a fixed slope slide.
But when electrons move they create a magnetic field. The magnetic field can’t be setup instantly though, and takes energy to exist. Takes a bit of time to setup the magnetic field, that is get electrons moving. This is called inductance. It’s sort like momentum, but doesn’t relate to mass.
So the electrons all start moving, great. But at two parts of the circuit, the light bulbs, they crash into a lot of atoms. It’s like a kid jamming a water slide. This is the resistance, this slows them down, creates a traffic jam. The means more electrons at they start of the light bulb, less at the end of it. Enter capacitance. This is basically static charge. When you have a lot of electrons in one spot, they repel each other. When you have an absence of them, it attracts electrons. This means the electric field is now reshaped. It drops quicker across the light bulbs, as they have resistance. And stops slower and barely at all across the wires.
This then feeds back up stream. The electric field alteration from this jam at the light bulbs goes back to the battery. This means the battery stop putting out so many electrons, because the electric field at the wire at the terminal is now weaker (meaning less voltage drops there). If you want to keep a slide analogy, your slide is now a wavy. Where it is steep, high voltage drop and strong electric field. Where it is shallow, low voltage drop and weak electric field.
The current then of course drops to match all throughout. From this effect. This then reduces the magnetic field, which again is not instant as it acts like momentum. This time resisting stopping. This then reduces the charge build up at the light bulbs, the capacitive build up goes away.
If the first light bulb took more voltage drop, it would let more electrons through. This would then cause a name at the second light bulb, which would back feed the electric field and cancel this out.
So a few microseconds later, it all sorts it self out. Electric field is at varying strength all along the circuit. Magnetic field is nice and steady all along it. This means the current is the same everywhere. The voltage is dropping across the light bulbs equally. They both receive the same power (assuming they had the same resistance).
So the electrons don’t do anything. They’ve moved far less than a millimetre by now. But the electric field and magnetic field rocketes around the circuit. They overshot, then over corrected and under shot, then overshot slightly less again, and then eventually became steady. This all ripples out until it is balanced. This is all communicated at the speed of light (or close enough). Any I’m balance one light bulb sees over another (which absolutely does exist when you first close the switch) equals itself out, as jams of electrons alter the electric field itself and propagate backwards to and weaker to strengthen the field at the other light bulb. This means the battery is driving a steady amount of electrons everywhere in the circuit. This means the voltage is equally distributed across both light bulbs. This is the steady state current and voltage you actually talk about. The steady state when you open and close the switch you don’t worry about. Well, not unless you’re an electrical engineer and you need to make sure the sparks flying from all this when the switch operates don’t fry something.
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