I recently completed my final for my first year electrical Engineering Subject and I have the image of the question above.
I was really confused because it says when both switches are open, which leaves the inverting input of the op-amp (-) disconnected and ungrounded, which I now assume the op-amp has an internal ground at its negative terminal? (I might be wrong) so this would make the inverting terminal =0 and the non-inverting a fraction of 5V. Therefore I would figure that the op-amp keeps turning up the voltage until its limit. How on earth can you select the resistors to match a Vb of 0.5V as the question asks for?
Maybe I am missing something with how the internal value of the op-amp works, please help.