- #1
fulmenatrum
- 10
- 0
So I've been trying to work on this project that requires me to take a 12V AC to DC adapter (says 300mA on it) and supply power to a CPU fan (11.8V, 0.57A) and several LEDS (20mA forward current, 3.2V). My question is what does the 300mA exactly mean as I thought that there was no such thing as a current source.
Also, I connected my CPU fan to a 9V household battery and an ammeter in series and received a current measure of 10mA. This apparently wasn't strong enough to turn the fan. But then I connected my CPU fan to a 12V Universal Battery (model: UB1250ZH) and the ammeter, still in series with the circuit read 500mA, which started to spin the fan rapidly. Now I'm quite doubtful that a difference in 3V is enough to increase the current by that much so I'm pretty sure that the 12V battery has some internal resistors working but I have no idea how and why it works the way it does. Also, why do these batteries have ratings on them like "0.75A" Does that mean it's the maximum current the battery can preform under? Are there variable resistors involved?
Thank you, any help will be very much appreciated.
Also, I connected my CPU fan to a 9V household battery and an ammeter in series and received a current measure of 10mA. This apparently wasn't strong enough to turn the fan. But then I connected my CPU fan to a 12V Universal Battery (model: UB1250ZH) and the ammeter, still in series with the circuit read 500mA, which started to spin the fan rapidly. Now I'm quite doubtful that a difference in 3V is enough to increase the current by that much so I'm pretty sure that the 12V battery has some internal resistors working but I have no idea how and why it works the way it does. Also, why do these batteries have ratings on them like "0.75A" Does that mean it's the maximum current the battery can preform under? Are there variable resistors involved?
Thank you, any help will be very much appreciated.