Hi, I am trying to make a 2amp 12VDC power supply adjustable. I was told to use a potentiometer. I need to know if this will work, and if so what size potentiometer to use. Any help will be appreciated.

Hi, I am trying to make a 2amp 12VDC power supply adjustable. I was told to use a potentiometer. I need to know if this will work, and if so what size potentiometer to use. Any help will be appreciated.
No it won't. Not the way you intend.
To get an adjustable power supply you require a REGULATOR CIRCUIT. That circuit can be controlled by a "normal" carbon based potentiometer.
The circuitry makes the output voltage stable, even under a variable current load.
.
The alternative is a high power (expensive!) wirewound potentiometer, which you connect to the 12 volt. The middle contact goes with the neutral / 0 contact to the ouput.
However : this potentiometer requires a lot of power (heat), and results in an unstable ouput voltage with varying loads.
.
Better build or buy a stabiliser circuit. Much less loss, less heat, and fully stable (adjustable) output voltage.
The circuitry can even be extended with current limitation that kicks in when maximum current limit is exceeded.
:)

Regulator is the way it should or could be done.
A Headlight Dimmer switch may work to 2 amps.