This historic engineering concept describes how well an insulating material allows the formation of an electric field within it. Standard engineering practice uses the term capacitance to describe the physical property of a component, while permittivity describes the specific material property. The original concept helped early electrical workers conceptualize how a dielectric enhances electrostatic induction compared to a vacuum.
Heard on the job
The original specification sheets for these paper capacitors list their permittance rather than capacitance.
Insider tip
The word has entirely fallen out of use in active engineering, replaced by capacitance for components and permittivity for materials.