What is the meaning of output voltage and current?

By | July 12, 2018

I have a 5V power supply with DC output rating: 5V @ 1500mA. It could power my High Torque servo very well.

I, however, have a fairly used 9V Alkaline battery. I shorted this battery and I measured the current to be ~3 Amps using a multimeter.

Later on, I connected this battery to a 5V regulator to power my High Torque servo, and it doesn't seem to be drawing as much power as my 5V DC power supply.

My question is, what does 5V @ 1500mA mean exactly? Is 1500mA the maximum current it draws or the minimum? If it's the maximum then my 9V battery seems to produce more current than the power supply, but that's not the case.

And why are power supplies not equally as powerful even though the voltage measure maybe similar.

My guess is that it all boils down to less internal resistance produces more current, and my 5V DC power supply has less internal resistance.

Is the internal resistance of my 5V DC power supply then: 5V / 1.5 A ?

Or maybe this doesn't even have anything to do with internal resistance.