Batteries

>>1026991
"it depends" is literally the answer, every scenario you described is completely different. However, you don't need to understand a whole lot to be able to figure out what happens when. But since you don't want to put in even that much effort,
>12V motor with 1.2V battery
The motor will start spinning at around 3V, so if you connect 2 batteries in series, it will start spinning. For full speed, you need 10 batteries in series, or a step-up converter, you can buy the latter on eBay around $1-$2. Step up converter makes higher voltage out of lower voltage, but they usually have 3V minimum working voltage
>9v battery, 5V usb
Ebay, step down converter
>12V car battery and 48V wheelchair
Just get another 3 car batteries or a single 48V one, a step up converter would work in theory, but in practice it would cost a lot because it needs to handle a lot of power
>nuclear reactor
now you're not even talking about volts but watts

For most devices, the voltage rating is fixed, a 12V device should be given 12V, a 5V device 5V; some exceptions are motors and heating elements that are listed with optimal working voltage. A 12V motor will spin at 3-4V, but very slowly, and will spin at 16V very fast, but will overheat and may burn out. LEDs should always be powered around the given ~3V.

Ah means amper hour, so if you have a 12V 1Ah battery and a motor that uses 1A at 12V, it means the battery will last exactly one hour. Wattage is voltage*amps, so a 12W motor operating at 12V will last 1 hour on a 1Ah 12V battery, 30 minutes on a 1Ah 6V battery and 30 minutes on a 0.5Ah 12V battery. From Ah you calculate how long your battery will last.

Read those 50 paragraphs and learn basic electronics, if you're really dense, play around with circuit simulators

>>1026991
It would help if you could link to specific examples of something you want to do. In particular, try to find examples of things you want to run, that list their voltage and current requirements.

>... How can I make the LED light up?
The simplified explanation:
To run one off of a wall outlet: you'd (me, at least) want to use a transformer to drop the AC volts down to ~6 volts, and then four diodes (1N4007) to make a full-wave rectifier.

"Plain"-style LEDs always need a dropping resistor connected to them, and they need to be connected to DC power with the polarity correct. Not doing either can instantly burn them out for good.

Consult the Google for "LED calculate dropping resistor" for pages to help with that.

>>1026991
>I have a 10MW nuclear reactor and a single 3v LED. How can I make the LED light up? What are the most simple basic ways that I can spend some time/money to make this happen? What are the side effects?

nuclear power is not analogous to a battery. nuclear power, or wind/coal/solar/hydro all create AC power. that's a larger subject than I feel like explaining, but in short, not the same as a battery.

an led has a forward voltage because it is a light emitting DIODE. This is the minimum voltage needed to get it to draw enough current to light up. It is not a purely resistive load such as a 3v tungsten bulb, which will react more or less linearly to the voltage applied.

like it's been said, the examples you list cover an incredibly wide range of subjects and really don't lend themselves to eli5 explanations.

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>>1026991
I hope this is not too complicated for OP. As for more details, if required.

>>1026991

Most of the "truths" in my post are approximate, simplified and not scientifically correct, but should help you understand batteries.

1) voltage is not the only parameter.
>A button cell that has 3V won't spin a 3V fan.
>Two AA batteries will spin a 3V fan.
Up to some current consumption each battery supplies what it's rated for.
Beyond some point, amperage increases and voltage drops.
Example 1: if you run a 3V motor with two AAA batteries, you're going to measure rather 2V than 3V on the batteries.
Example 2: If you short-circuit a 9V cell, you're going to measure zero volts, and some current will flow.

2) If your device requires higher voltage, it will not work as expected. Motors go slower, incandescent bulbs shine darker, most electronic devices detect undervoltage and shuts off (brow-out detection).

3) If your device requires lower voltage, it will probably get damaged. Motors may overheat or short-circuit, incandescent bulbs die, electronic burns (usually).

4) Decreasing voltage: either put something to eat excessive voltage (resistor, LDO), or convert the voltage.

5) Increasing voltage: you need to convert voltage.

6) Converting DC-DC voltage is typically: switch on/off input, store energy in a capacitor/coil, flatten the output.
Converting has efficiency from 90% to almost 100% depending on various parameters.
That is: you can go down from 1.1A 12V to 2A 6V, or up from 2.5V 6V to 1A 12V.

You can get, let's say, 100V from a 1.5V button cell (switching capacitors cascade will do), but you'll get almost no usable current. You can go from 100V down to 1.5V and have enough amperage to weld (ok, 1.5V is too low, I know).

>>1027578
...continued

Now, your examples:

> I have a single AAA battery and a 12v motor. How can I make the motor spin?
Single AAA battery is too little to step up from, at least if you want to power anything with high current demands.
MCP1640 can go up from a single AAA battery.

> I have a 9v battery and a 5v USB drive. How can I get it to show me my porn? What are the most simple basic ways that I can spend some time/money to make this happen? What are the side effects?
Your drive needs at least 0.4A. 9V battery can supply 0.05A if you've got a good one.
Otherwise, LDO: L7805 or similar, switching: almost any step down will do. An example that I've used recently: NCP3170.

> I have a 12v car battery and a 48v wheelchair motor. How can I make the wheelchair go forwards? What are the most simple basic ways that I can spend some time/money to make this happen? What are the side effects?
Step up converter; boost converter. If tour wheelchair will need 2A, your car battery will have to supply at least 10A (efficiency reasons). Sounds still fine for a car battery, but it'll discharge fast. Disadvantage: you need a coil that survives high currents. Big and expensive. And external switching transistors and an external diode, all of these expensive if good.

> I have a 10MW nuclear reactor and a single 3v LED. How can I make the LED light up? What are the most simple basic ways that I can spend some time/money to make this happen? What are the side effects?

Your nuclear reactor generates not that high voltage; probably 600V (it it's 10MW, that is not impressive at all). Generators use that low voltage, for it's hard to insulate coils that it is made of.
Your generator supplies AC, not DC; you can use a transformer to get any voltage from any voltage. Literally. Get 6VAC, rectify, flatten with a capacitor, use LDO to cut it to 3V, there you go. It's less expensive than car battery to wheelchair motor.

It's not fallout or gilligans island. You decide what needs to be powered and then find a suitable power source, or vice versa. If I need to power some leds I'll find the the voltage needed and mix the less to they match or are divisible by a voltage. Say an led needs 4.5 volts, you could use 4 AAs in series to reach that (4x1.2 equals 4.8) and throw a resistor in front, or you could use 2 leds in series(4.5x2=9) and use that with a 9 volt.

Most things fall into a range, like 3.7 to 5.2 volts or 11.5-14.3 volts and you can find a power supply in that range and manipulate it slightly to work. A 12 volt car battery is actually 12.7 volts when charged and charges at around 14.3 usually, a cellphone battery is 3.7 bit charged is 4.2 and can charge off a 5 volt supply.

But that's only a piece of the puzzle, amperage is the workhorse. You could in theory use 12 AA batteries to power a car, but the starter would flatten them before it even turned most likely. Some car batteries can deliver 700 amps at once when allowed, AAs cant.

Guys, you realise this is OP's homework, right?

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>1.
A single AAA battery won't provide enough current or voltage to reliably spin the motor. They're 1.5 V. They vary by manufacturer, but you may not want to draw more than 0.25 A from a single battery.
>2
... I've either taken the bait or you're clinically retarded. Seek help.
>>1028525
Yes, which he clearly hasn't googled, or bothered to read the information that is given to him. I'm not spoon feeding this prick, who hasn't even stated what exactly is not understood about the paragraphs 'that quote the entire book of thermodynamics'
Basil goes in all fields.
basil.

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>>1027564
>mystery ebay volt eater

>>1028525
It took me a while to realize that some part of the world does not have the summer vacations right now...