Capacitance is the property that permits electrical energy to be stored in a dielectric between two conductors that are at different potentials. Capacitance is dependent on the ratio of the inner and outer conductor dimensions and the dielectric constant, but in an opposing way from impedance. Thus as capacitance decreases in cables of equal dielectric constant, impedance increases. Capacitance is expressed in picofarads 10-12 farad) per foot.