Note: The symbols for electrical contact specific terms i.e. contact area, contact resistance, etc. have been retained from the german version of the Data Book. In related English literature some of them may vary using subscript symbols related to the language used – for example “contact resistance”: as used here from german R<sub>k</sub>, in english mostly R<sub>c</sub>.
*<figtable id="tab:Übersicht der Begriffe und deren Erklärung"><caption>'''Electrical contactOverview of terms and formula symbols''' <br /caption>is a property which is generated through the touching of two electrically conducting surfaces.
*'''{| class="twocolortable" style="text-align: left; font-size: 12px"|-!Term!Formula symbol!Unit!Explanation|-|Electrical contact|||A property which is generated through the touching of two electrically conducting surfaces|-|Contact part''' <br />is a |||A metallic component which is designed to create or interrupt an electrical contact (is frequently replaced by the term “contact” if it is clearly understandable that a physical piece or item is meant)|-|Contact area|||The whole area on a contact part that may be used for contacting|-|Apparent contact area|A<sub>s</sub>|[m<sup>2</sup>]|The part of the contact area on contact parts that can make physical contact during the touching of two contacts|-|Load bearing contact area|A<sub>t</sub>|[m<sup>2</sup>]|The part of the apparent contact area which is affected by the contact force.It is the sum of all microscopic actual touching points|-|Effective contact area|A<sub>w</sub>|[m<sup>2</sup>]|The part of the load bearing contact area through which current is flowing and therefore the sum of all current carrying touching areas (a-spots), Aw < At < As|-|Contact resistance|R<sub>k</sub>|[Ω]|Composed of the constriction resistance and the film resistance|-|Constriction resistance|R<sub>e</sub>|[Ω]|The incremental electrical resistance generated by the constriction of the currents paths in the touching area (a-spot)|-|Film resistance |R<sub>f</sub>|[Ω]|Generated by a foreign matter layer, which for ex. is formed by a reaction of the contact material surface with the surrounding atmosphere (a surface film is a substance on the contact surface with different properties than those of the actual contact material)|-|Path resistance|R<sub>d</sub>|[Ω]|the total electrical resistance between reference points (usually the device terminals) which can be freely chosen but must be defined. It is the sum of the conductor resistance R<sub>b</sub>and the contact resistance R<sub>k</sub>|-|Contact Force|F<sub>k</sub>|[N]|The force that is exerted between the two contact parts in the closed position|-|Contour area|A<sub>n</sub>|[m<sup>2</sup>]|The contiguous area which includes all effective a-spots, Aw < An < As ; An ≠ At|-|Radius|a|[m]|Radius of the circular effective contact area|-|Elastic modulus|E|[MPa]|Material characteristic value from materials engineering that describes the proportional relationship between stress and strain during the deformation of a solid body in the case of linear-elastic behavior|-|Hardness (Brinell or Vickers)|H||The mechanical resistance that a material offers to the mechanical penetration of another body|-|Current|I|[A]|The electric current strength indicates how much electric charge moves through a conductor per second|-|Number of effective individual contact areas|N|||-|Electrical resistance|R|[Ω]|In electrical engineering, electrical resistance is a measure of the electrical voltage required to allow a certain electrical current to flow through an electrical conductor (component, circuit)|-|Radius contact area|r|[m]||-|Path resistance|R<sub>d</sub>|[Ω]|The total electrical resistance between reference points (usually the device terminals) which can be freely chosen but must be defined. It is the sum of the conductor resistance Rb and the contact resistance Rk|-|Distance of the effective single contact areas between i and j|sij|[m]||-|Maximum contact temperature|T<sub>Kmax</sub>|[K]||-|Voltage|U|[V]|The greater the electrical voltage, the more charge can be transported and thus the electrical current strength, i.e. the amount of charge, also increases.|-|Contact Voltage|U<sub>K</sub>|[V]|The electrical voltage created when two different substances come into contact. This is ultimately caused by the different electron levels in the materials|-|Volume|V|[m<sup>3</sup>]|The volume is the spatial content of a geometric body|-|Specific resistance|ρ|[Ω*m]|The resistivity (Rho) is defined as the resistance of a conductor of 1 m length and 1 qmm cross-section (A) at a temperature of 20 degrees Celsius|-|Lifting Force|F<sub>A</sub>|[N]||-|Frictional wear|||The loss of material caused by mechanical wear between contact parts|-|Bounce|||The single or multiple interruption of conduction between contact parts during the make operation caused by alternating transformation of kinetic to potential energy|-|Contact Wear|||Includes all changes on a contact surface. Mechanical and electrical wear must be distinguished|-|Material transfer|||The transfer of contact material from one contact part to the other. It occurs mainly during switching of DC loads. The direction of the transfer depends on the load circuit properties and the contact materials used|-|Arc erosion|||The loss of material into the surrounding of the contact spot which is generated by electrical arcing. It occurs during contact make as well as break operations|-|Contact welding|||Occurs when melt-liquefied touching areas of the contact parts come in contact with each other. The melting occurs during high current carrying through these areas. During make operations this occurs through bounce arcs, on closed contacts a too high contact resistance or dynamic separation of the contacts due to high short circuit currents can cause the welding of the contacts. The welding then may cause a device failure if the device specific opening forces cannot break the weld connection|-|Arc movement|||Happens when during the break operation a sufficiently high magnetic field is generated which exerts a force on the electrical arc which is then moved from the originating spot towards an arc chute (or arc splitting plates)|-|Arc extinguishing|||Means the process of letting the current go to zero and transferring the arcing gap from a conducting to the non-conducting stage. Selecting the most effective extinguishing measures depend mostly on the current characteristics, the current value and the circuit voltage|-|Recovery|||of an arc gap during contact opening is defined as the process of the electrically conducting plasma of an arc losing its electrical conductivity after reaching current-zero|-|}</figtable>
*'''Contact area''' <br />is the whole area on a contact part that may be used for contacting.
*'''Apparent contact area A<sub>s</sub>''' <br />is the part of the contact area on contact parts that can make physical contact during the touching of two contacts.
*'''Load bearing contact area A<sub>t</sub>''' <br />is the part of the apparent contact area which is affected by the contact force. It is the sum of all microscopic actual touching points.
*'''Effective contact area A<sub>w</sub>''' <br />is the part of the load bearing contact area through which current is flowing and therefore the sum of all current carrying touching areas (a-spots), A<sub>w</sub> < A<sub>t</sub> < A<sub>s</sub>.
*'''Contour area A<sub>n</sub>''' <br />is the contiguous area which includes all effective a-spots, A<sub>w</sub> < A<sub>n</sub> < A<sub>s</sub> ; A<sub>n</sub> ≠ A<sub>t</sub>.
*'''Contact resistance R<sub>k</sub>''' <br />is composed of the constriction resistance and the film resistance.
*'''Constriction resistance R<sub>e</sub>''' <br />is the incremental electrical resistance generated by the constriction of the currents paths in the touching area (a-spot).
*'''Film resistance R<sub>f</sub>''' <br />is generated by a foreign matter layer, which for ex. is formed by a reaction of the contact material surface with the surrounding atmosphere (a surface film is a substance on the contact surface with different properties than those of the actual contact material).
*'''Path resistance R<sub>d</sub>''' <br />is the total electrical resistance between reference points (usually the device terminals) which can be freely chosen but must be defined. It is the sum of the conductor resistance R<sub>b</sub> and the contact resistance R<sub>k</sub>.
*'''Contact force F<sub>k</sub>''' <br />is the force that is exerted between the two contact parts in the closed position.
*'''Frictional wear''' <br />is the loss of material caused by mechanical wear between contact parts.
*'''Bounce''' <br />is the single or multiple interruption of conduction between contact parts during the make operation caused by alternating transformation of kinetic to potential energy.
*'''Contact wear''' <br />includes all changes on a contact surface. Mechanical and electrical wear must be distinguished.
*'''Material transfer''' <br />is the transfer of contact material from one contact part to the other. It occurs mainly during switching of DC loads. The direction of the transfer depends on the load circuit properties and the contact materials used.
*'''Arc erosion''' <br />is the loss of material into the surrounding of the contact spot which is generated by electrical arcing. It occurs during contact make as well as break operations.
*'''Contact welding''' <br />occurs when melt-liquefied touching areas of the contact parts come in contact with each other. The melting occurs during high current carrying through these areas. During make operations this occurs through bounce arcs, on closed contacts a too high contact resistance or dynamic separation of the contacts due to high short circuit currents can cause the welding of the contacts. The welding then may cause a device failure if the device specific opening forces cannot break the weld connection. <br />
*'''Arc movement''' <br />happens when during the break operation a sufficiently high magnetic field is generated which exerts a force on the electrical arc which is then moved from the originating spot towards an arc chute (or arc splitting plates).
*'''Arc extinguishing''' <br />means the process of letting the current go to zero and transferring the arcing gap from a conducting to the non-conducting stage. Selecting the most effective extinguishing measures depend mostly on the current characteristics, the current value and the circuit voltage.
*'''Recovery''' <br />of an arc gap during contact opening is defined as the process of the electrically conducting plasma of an arc losing its electrical conductivity after reaching current-zero.
*'''Symbole used'''
<xr id="fig:Symbole used"/>
<figure id="fig:Symbole used">
[[File:Symbole used.jpg|right|thumb|Symbole used]]
</figure>
==References==
[[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]]
[[de:Begriffe]]