The battery thing works in a pinch- some devices let’s say they take 4aa but you only have 2? You can use foil or paper clips or wire across the empty slots and they might work. There’s a few catches though. When it works- you’re unlikely to get as much use time out of the device on the cell. You also need to be careful. Sensitive devices may not work right or at all- and can even be damaged. Likewise you can damage batteries this way- especially rechargeable cells. With some math we can figure out the voltage, amperage, internal resistance and other factors to configure cells in a way that can work for our purposes. But non rechargeable batteries and simple circuits can be powered this way in a pinch with little risk.
In almost all cases, you need to use the same number of cells. Pretty much anything with a circuit (TV remote, old game boy, etc) needs a certain voltage. A flashlight or something would work with a lower voltage, but it would be dimmer.
All alkaline cells have 1.5v nominal, so AA and AAA are somewhat interchangeable for low load applications. The difference is the bigger cells have a higher capacity and can handle a higher discharge rate.
Mostly true. But it can be more complex and also depends on wether you’re substituting smaller cells for larger capacity cells, or omitting cells and using a conductor to complete a circuit- or rigging a battery bank. A series or parallel configuration can change the voltage or amperage. With exception of more complex electronics or those with self diagnostics- dropping cell capacity (and amperage) won’t do much besides reduce your run time- however if the amperage is too low it will not be sufficient for meaningful use of the device.
Using most consumer batteries 1.5v to 1.5v you won’t see a change in voltage if you keep the default configuration and number of cells- but if you change the number of cells such as by using a conductor to “jump” terminals because of insufficient number of cells- or because you can fit more of a smaller cell- an increase or decrease in voltage can be seen depending on configuration. Increasing amperage or voltage can damage electronics- especially small or sensitive ones, and a decrease can reduce performance or cause malfunction. Something like a DC motor can be greatly effected for instance. The more complex the electronics the more things like internal resistance of the cells or battery bank, or battery capacity matter. With rechargeable cells or a system that feeds back to the cells this can be critical as smaller cells can overheat, internal cell resistance out of range can cause malfunction or damage- etc.
So as said- simple consumer electronics powered by disposable 1.5v “common” batteries are generally but not always safe to use various battery “tricks” on for those without a grasp of electrical principals or math. You can even configure battery banks of different cells like AA to produce theoretically as much or as little voltage as you want if you have enough, some other minor supplies, and some know how.
Using batteries, resistors, wire, diodes, and other simple electronic components you can string almost any type of cells together and produce desired outputs in most of the “meat and potatoes” specs like voltage and amperage. When you start getting to a point where you need an oscilloscope to confirm specs- such as where a “clean” or other specification for power input is needed to a much more precise level- it can get way more complex- but electricity is (outside far flung high level stuff) pretty simple in theory. It’s just math for the most part, and understanding how and where to apply what math. So you can do a lot with almost any power source with enough infinity. Powering the remote with 2aaa instead of 2aa isn’t exactly rocket science- and you don’t need to do any math more than likely- but it never hurts to get the practice and understand the why and not just the how.
Replacing one or more batteries with wires, thus reducing the voltage, reduces the wattage delivered to the device. I use this to slow down the motor in vibrators.
Yes. Increasing or decreasing voltage or amperage isn’t always undesirable. Simple devices like non precision motors you are usually pretty safe changing current to without checking. Generally you won’t damage a motor by running too little power to it- but if increasing power you should be careful. You can also fairly easily add the simple and cheap electrical components to most consumer low voltage electronics to allow on demand modulation up to maximum supplies voltage/amps.
All alkaline cells have 1.5v nominal, so AA and AAA are somewhat interchangeable for low load applications. The difference is the bigger cells have a higher capacity and can handle a higher discharge rate.