How can I use a potentiometer to control fixed DC Voltage?

Question

I have a 12V, 800mA DC Adepter. I want to use it as a variable voltage supplier, then how can a potentiometer be use for varying that 12V? A simple application(connecting output of adepter to fixed terminals of potentiometer as input , any of fixed terminals and terminal of slider as output) doesn’t work for high load application (I > 0.3A) . By doing this sparking appears in potentiometer and it burnout.

Answer 1

USe this circuit, and put your potentiometer in place of R1 and R2.
http://www.tkk.fi/Misc/Electronics/circuits/lm317.html

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