Bulb Replacement

Bob wants to replace all the faulty bulbs in his house. He chose a very special way to do that. He puts all the bulbs($N$ in number) in a container. Now in each turn he randomly selects a bulb from the container. If the bulb is faulty, then he replaces the faulty bulb with a working bulb i.e. he throws the faulty bulb and puts a working bulb in the container. If the bulb he selects is working, he