My external HDD reader power brick broke (12V 2A) so I’m switching it with a spare power brick (12V 3A). Is that safe?
yes, the 3A brick can supply up to 3 amps, so you’ll just be under utilizing it.
be sure to check the polarity or the dc connection matches your old brick.
Voltage always has to be the same.
Amperage always has to be equal or higher.
note these two rules and you’ll always be good.
And indeed check the polarity of the connector (inside is almost always positive +) yet not always.
I like to think of volts like the pressure in a pipe. Too much and you’ll burst something, too little and it won’t work.
Amps are like the flow of water in a pipe. You only need enough flow to get your device to work. Your device will only use what it needs so too much isn’t necessarily a problem here as long as your pressure (Volts) isn’t too high.
99% of the time you will be fine with the same voltage and higher amperage. That 1% is when you are trying to power something that is poor quality and the power circuit is designed wrong. Most devices are designed so the pull what amperage they need and no more. Poorly designed devices will let everything through and it’ll blow up.
This is why we can put 1000W power supplies in computers. The system pulls what it needs, but the power supply is capable of providing 1000W.
I wonder if the same theory holds true with, say, a 100A power supply? Probably.
Yes except for LEDs.
Light Emitting Diods act like diods in the first place alowing for a very high current flow. There are circuits to limit the current automatically, but more often then not, an inline resistor is the much better choice.
“With water flow analogy we can imagine the electric current as water current through pipe, the resistor as a thin pipe that limits the water flow, the voltage as height difference of the water that enables the water flow.”