===<!--6.4.2 -->Contact Physics – Formulas===

*'''Constriction resistance''' : <br /math>Re R_e = D\rho/2a</math>

Re : <math>R_e = D\rho/2Na</math>

Re : <math>R_e = D\rho/2 x E ai \sum a_i + 3B D3 \pi \rho /32N² 32N^2 x E E \sum \sum (sijs_ij) i = \neq j</math>

*'''Contact Path resistance''' : <br /math>RK R_d = Re R_b + RfR_K</math>

*'''Path resistance''' <br />Rd = Rb + RK *'''Contact resistance and contact force''' : <br /math>R R_K = 280D ³ 280\rho \sqrt[3]{E(F · F_K \cdot r) K K} </math>

deformation of the contact material; F _k < 1 N for typical contact materials) kRK : <math>R_K = 9000 D \rho \sqrt{ H/ FKF_K}</math>

deformation of the contact material; F _k > 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_A in N and l in kA) *'''Contact voltage and max. contact temperature''': <math>T_kmax \approx 3200 U_K</math>

*'''Contact voltage and max{| class="twocolortable scalable" style="text-align: left; font-size: 12px; width:45%;"|-!Material combination !c|-|Copper - Copper |(0. contact temperature''' 08 bis 0.14) x 10^-3|-|Aluminum - Aluminum|(3 bis 6,7) x 10^-3|-|Brass - Brass |0.67 x 10^-3|-|Steel – Silver|0.06 x 10^-3|-|Steel – Copper|3.1 x 10^-3|-|Steel – Brass|3.0 x 10<sup>-3<br /sup>T kmax 3200 UK|}

*'''{| class="twocolortable scalable" style="text-align: left; font-size: 12px; width:45%; "|-!Contact resistance at higher contact forces shapes !m|-|Flat – Flat |1|-|Pyramid – Flat|0.5|-|Sphere – Flat |0.6|-|Sphere – Sphere|0.5|-|Multi-strand brush - Flat|1|-|Current bar (according to BabikowBusbar)''' <br />R = cF contact|0.5 -m K K0.7For F between 10 and 200 N K|}c <div class= material dependent proportionality factorm = shape dependent exponent of the contact force"clear"></div>

[[Application Tables and Guidance Guideline Data for the Use of Electrical ContactsContact Design#References|References]] [[de:Formeln_aus_der_Kontaktphysik]]