A 10 Ω lightblub is connected to a variable voltage source. The way to vary the voltage of the source is not by altering the source itself, but rather by altering the internal resistance of the source, thus changing the terminal voltage, Vab. If the internal resistance of the source were zero, the termal voltage would be 120 V, and at some value r, the power output by the lightbulb is 100 W.
(a) What is the terminal voltage, Vab?
(b) If the terminal voltage were doubled, what would be the power output by the lightbulb?
(c) What is the internal resistance, r, of the lightbulb when the power output is 100 W?