Regarding LDR in circuit

sir why do we connect one end of LDR from A0 and one end from GND.


We have answered a similar question on the forum -

look first of all one end of ldr is connected with 3v3 and another with analog pin i.e. A0 then a resistor is connected in series i.e. one end of resistor will be A0 and another at ground . so its like you are placing 2 resistors one ldr and one 10k resistor in series and supplying voltage (3v3) and compleating circuit (by connecting to ground) and in between you are measuring voltage change (by analog pin) . since light will affect the resistance of ldr hence voltage will change.