Can I use this Dell AC adapter on a different kind of Dell?

I’ve heard that sometimes an adapter will work for a different type of laptop than you bought it for, but only if the voltage and wattage requirements for the different laptop are lower than or equal to the max amount the charger you’re using is able to deliver… at least that’s what I thought I was hearing. First the explanations I found seemed to make sense, but then it got more confusing when I heard:

“so if charger Voltage is greater than computer Voltage, don’t try it

but if charger Amperage is greater than computer Amperage, computer will only use the Amperage it needs and it’s ok

is that right?”

And the answer was:

“Basically, yes.”

Source:
http://www.dslreports.com/forum/r21830410-Interchangeable-chargers-for-Dell-laptops
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I’m not sure if I get how amperage works. Is what they said true?

The charger I already have is Voltage 20V and Wattage 90W. The charger specifically designed for the other laptop I want to use it on would be Voltage 90V and Wattage 65W. Do I need to get that other charger, or can I use the one I already have?

If it helps anyone answer the question, the charger I already have is for a Dell Inspiron 8200 and the computer I’m wanting to know if I can use it on is a Dell Latitude D600.