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This paper investigates the synergetic effect of the SF6-N2 gas mixture, taking the effective temperature of the free electron Maxwell spectrum at the time of breakdown as an independent parameter. In this way, a direct link between a macroscopic variable (dc breakdown voltage of the mixture) and a fundamental microscopic variable (effective temperature) is established. Derivations are presented of expressions that relate the streamer mechanism breakdown voltage in an SF6-N2 gas mixture to the pd product (pressure×interelectrode distance), the percentage contribution of the N2 gas (χ), and the effective temperature of the spectrum of free electrons in the mixture (Td) at the time of breakdown (breakdown temperature). A new theoretical model for the dependence of the electron attachment coefficient (effective cross section) in the electronegative SF6 gas was used, which resulted in the final expression being different from the corresponding expressions obtained from other models. The obtained results were verified by experiments, under well controlled laboratory conditions. There was a high degree of agreement between the experimental and the theoretically calculated results.