 To do this, the heat transfer at each surface is expressed as
where "R""i" = (1 − "ε""i")/("A""i""ε""i") is the resistance of the surface.Likewise, "M"e,"i"° − "J"e,"i" is the blackbody exitance minus the radiosity and serves as the 'potential difference'.These quantities are formulated to resemble those from an electrical circuit "V" = "IR".