I can't understand some stuff about op-amps. Here is my list of doubts:
If an op-amp amplify the difference between the V+ and the V-, how can it work if for the principle of virtual ground V+ = V-, and so if V+ = V- there aren't difference to amplify.
Considering this circuit as the ideal one of the op-amp, why V+ = V- ? Why does the principle of virtual ground exist? Why is the voltage on V+ is equal to the one in V- ?
Is correct to say that all the Vin applied on this equivalent circuit will fall on the Ri?
Take a look at this circuit, my teacher says that I1 is equal to I2, but I can't understand why:
If the two resistor have respectively a knot to mass, the only condition when I1 = I2 is when Vin = Vo and when R1 = R2
The I1 and the I2 that will go to the point of the virtual ground (the point marked on this photo), where will they go at the end? Will they go to the physical ground?