There are three parts to the following question about electrical circuits... First, when there is one light bulb in a circuit, parallel or series, and you unscrew the lightbulb, there is no more current but the base of the unscrewed lightbulb (the part that's connected to the circuit, not the actual bulb) still has voltage. Why? Secondly, there are two light bulbs in a series circuit and one is unscrewed (again there is no current in the circuit), but there is still voltage in the unscrewed lightbulb base, while there is no voltage in the lightbulb that is screwed in, no matter what order the two lights are in the circuit. Why does this happen? Lastly, if you have two light bulbs in a series circuit and remove them both, there is no voltage in any of the bases. Why is there no voltage when you remove both clight bulbs, but there is voltage when you only remove one?