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*'''Constriction resistance'''
: <math>$R_e = \rho/2a</math>$
(Single spot contact according to Holm; circular touching spot between clean
contact surfaces)
: <math>$R_e = \rho/2Na</math>$
(Multi-spot contact according to Holm without influence between the N
individual spots)
: <math>$R_e = \rho/2 x \sum a_i + 3 \pi \rho /32N^2 x \sum \sum (s_ij) i \neq j</math>$
(Multi-spot contact according to Greenwood considering the influence between
the spots)
*'''Contact resistance'''
: <math>$R_K = R_e + R_f</math>$
*'''Path resistance'''
: <math>$R_d = R_b + R_K</math>$
*'''Contact resistance and contact force'''
: <math>$R_K = 280\rho \sqrt[3]{E (F_K \cdot r)} </math> $
(According to Holm model for film-free spherical contact surfaces with plastic
deformation of the contact material; F<sub>k</sub> < 1 N for typical contact materials)
: <math>$R_K = 9000 \rho \sqrt{ H/ F_K}</math>$
(According to Holm model for film-free spherical contact surfaces with plastic
deformation of the contact material; F<sub>k</sub> > 5 N for typical contact materials)
*'''Dynamic contact separation''' (without considering magnetic fields caused by the current path)
: <math>$F_A \approx 0,8 xl^2</math>$
(Rule of thumb with F<sub>A</sub> in N and l in kA)
*'''Contact voltage and max. contact temperature'''
: <math>$T_kmax \approx 3200 U_K</math>$
*'''Contact resistance at higher contact forces (according to Babikow)'''
: <math>$R_K = cF_k^{-m}</math>$
For F<sub>K</sub> between 10 and 200 N<br/>
c = material dependent proportionality factor<br/>
