L200c power supply, pot won't go down to 0 ohms
The datasheet shows you how to do it properly.



Figure 23. Programmable Voltage and Current Regulator.

You've already run into the limits of the pot resistance at each end. The other problem to watch is current through the track. For example, a 100 Ω, 1 W pot can take $$ I = \sqrt {\frac {P}{R} } = \sqrt {\frac {1}{100}} = 100 mA~max $$ This is the maximum current that any part of the track can handle. Don't, for example, think that because you are at 50% setting that it can handle 200 mA.

The Figure 23 solution uses the pots as a control signal. The end of track resistance should be negligible on a 10k or 100k pot.


  [OP's question:] Will this work with any opamp or do i need to use the 741?


The 741 was one of the early opamps and nearly anything made since then would be better. Read the datasheet note about connecting point 'A' to a negative supply if you want to get the output down to 0 V. Other than that, just check the operating voltage and how close to the supply rails the device is able to get.