Can I connect a resistance directly between 5V and A0 of the board and reed the output ?
When you put a potentiometer across 5V and 0V and the wiper to analog pin, which is a very common thing to do, and turn the pot to one extreme, you are actually connecting the pin to 5V anyway.
Can I connect a resistance directly between 5V and A0 of the board and reed the output ? Or will it burn the arduino ?
Beginners often think that a single resistor will drop a voltage across it. It will not.To drop a voltage you need current through it and if you simply connect a resistor of what ever value to between 5V and a measuring device you will see 5V....
so... for example a resistor at an op-amp input will have the same voltage at either end of itself ?