Like I understand wattage and that a light bulb uses way less watts than say an electric dryer. But what causes less current to be supplied to the light bulb vs the dryer? I assume the power being supplied by the grid wants to force electricity out at a constant rate. So what is built into various circuits that causes the appliance to accept current at a higher or lower load? Is it simply just resistance? I can’t seem to wrap my head around this one.
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>Like I understand wattage and that a light bulb uses way less watts than say an electric dryer. But what causes less current to be supplied to the light bulb vs the dryer? I assume the power being supplied by the grid wants to force electricity out at a constant rate. So what is built into various circuits that causes the appliance to accept current at a higher or lower load? Is it simply just resistance? I can’t seem to wrap my head around this one.
There is no forcing and no rate The power grid just provides a voltage and as much current as the load desires. The load **determines** the current, it doesn’t “accept it”.
It’s really super simple. If you connect a load with an equivalent resistance of 12Ω to 12V it will draw 1A, period.
If the dryer has an equivalent resistance of 20Ω and you connect it to 220V it will draw 11A.
You can then put a power supply in-between that limits the current that’s “let through” or varies the operating voltage or maybe put some breakers and fuses in that will pop/blow when the current draw exceeds the limit of the wiring, but the concept doesn’t change.
edit: ignore me, I don’t know what I am talking about (well, I have some clue, but am not explaining it correctly)
~~There is a fixed relationship between voltage, current and load (resistence).~~
~~The voltage is essentially fixed, the load is set by the device concerned (which can vary depending on how much work is being done e.g. stage of washing cycle, more constant with a light bulb unless efficiently dimmable).~~
~~Thus, the current is different between devices (and between stages of their operation) to balance out the equation between voltage, resistence and current.~~
~~Voltage is equal to current times resistence.~~
~~https://www.allaboutcircuits.com/textbook/direct-current/chpt-2/voltage-current-resist~~
~~The above is about direct current but this is also true in an AC circuit when the alternating current and voltage are in phase. That is, when the circuit is resistive.~~
~~https://electrical-engineering-portal.com/basics-power-alternating-c~~
You’re all making very great points. I appreciate all this. One more question I’ve come up with now that this discussion has been brewing.
If every consumer of electricity on a grid suddenly decided to flip the main breaker to their home, businesses, warehouse, etc. at the simultaneous EXACT same time, without notifying the utility provider, what would that do to the grid? Would power lines overload from all the electricity currently being pumped via power plants and cause the grid to collapse, explode, what have you?
Imagine your attic is full of marbles. Those marbles are static because the floor is stopping them from falling into your house.
Imagine you drill a hole in your ceiling, now the marbles start falling. How fast they hit the floor is determined by how tall Your ceiling is. If you make the whole bigger, the balls don’t fall faster but more balls fall down.
In this (imperfect) analogy, the ceiling height is the voltage differential (120V for US) and the number of balls falling is the current (electrons). You can see how the current is only affected by the size of hole and not by how many marbles are actually in the attic.
Your appliance is analogous to the size of the hole so a small hole (light bulb) will only allow a small current and a big hole (a dryer) will allow tons of marbles.
>Is it simply just resistance?
Yes. Voltage is set, the only thing that can vary is intensity, and you can make that change by modifying resistance.
You only need 2 formulas: V=R.I (ohm’s law) and P = V.I (watts). You can asssemble them and have P = V² / R , or P = I²R .
Your typical resistor in an electronic circuit is rated for 0.25W heat dissipation, because it is not supposed to heat, only to filter signals. There are bigger resistors that can take some heat typically used in CRT screens or race cars shutoff systems. They usually dissipate up to 10W.
But there are other kind of resistors, specifically made to dissipate a ton of heat. The one in your oven that goes bright red usually has a 25ohm resistor value, meaning applying 230V to it creates a circuit that needs to dissipate about 200W. Your head dryer does something similar.
electronic cigarettes resistors use the same property, except they work with 5V or less, so they need to have lower values. I made some that went under 1ohm when I was vaping. The material is specific, it used to be kanthal but there are other alloys.
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