4.2 Capacitance btwn two conductors Note that an isolated conductor certain restrictions (1)In reality, a conductor is always under influence of the environment So it's difficult to isolate a conductor (2 )An isolated conductor has a small C. For instance a conductor of the size of the earth r=64×10°m, C=4丌0R=7×10 4 F Thus, we need capacitors consisting of two conductors