No you don't. The only types of microphone in the world that need power to run are Condensers and Ribbons. Even then they are only using dc voltage to piggy back the audio signal down the line.
Edit: To clarify between a line in and a mic in. Mic in's almost always use a 3 pin xlr balanced connector and an cable running at -4dBV. A line in, such as an input for a guitar or any household consumer audio equipment runs on 2 pin jacks and cables, and run at +10 dBV.
However using a mic in that input isn't ideal at all. The voltage will be so low from a dynamic mic (one that most consumers use and self generates an electrical signal using a moving iron bar surrounded by copper coils) that in order to get an audible signal you will have to boost the input so much it will be ridden with noise and possibly distortion.