Since you are all starving students, and you hate paying your power bills to Duke energy, you and your roomates have the bright idea of setting up an...

Since you are all starving students, and you hate paying your power bills to Duke energy, you and your roomates have the bright idea of setting up an excercise bicycle to generate power to provide lighting while you are studying for this class. The way this works is that one by one each of you pedals the bicicycle, which lights a 100 Watt light bulb over the kitchen table in a different room where all of the other room-mates are studying. It is your turn and you work hard at pedaling the bicicyle and all is well for the first 15 minutes. 

Suddenly something happens so that you immediately know that the light bulb has burned out. Remember that you can't see the light bulb from where you are pedaling the bicycle, and you can't hear the yells of dismay from your room-mates. What has occured which gives you this information?  

Suppose that one of your room-mates has the bright idea to plug another 100 Watt light bulb into the socket which powers the 1st light bulb from the bicycle so that he can have his own light. How could you immediately tell that your room-mate is playing a trick on you even if you are in a different room?