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Contact resistance values are typically small (in the microohm to milliohm range). Contact resistance can cause significant voltage drops and heating in circuits with high current. Because contact resistance adds to the intrinsic resistance of the conductors, it can cause significant measurement errors when exact resistance values are needed.
If the resistance is not constant, the previous equation cannot be called Ohm's law, but it can still be used as a definition of static/DC resistance. [4] Ohm's law is an empirical relation which accurately describes the conductivity of the vast majority of electrically conductive materials over many orders of magnitude of current.
This equation, along with the continuity equation for J and the Poisson's equation for E, form a set of partial differential equations. In special cases, an exact or approximate solution to these equations can be worked out by hand, but for very accurate answers in complex cases, computer methods like finite element analysis may be required.
The mirror circuit of Fig. 5 forces the drain current of M1 to equal the input current and the output configuration assures that the output current equals the drain current of M2. Expanding equation (8) in a two-variable Taylor series about and truncating after the first linear term, leads to an expression for the mismatch of the drain currents ...
A generalization of the Landauer formula for multiple terminals is the Landauer–Büttiker formula, [5] [4] proposed by Markus Büttiker [].If terminal has voltage (that is, its chemical potential is and differs from terminal chemical potential), and , is the sum of transmission probabilities from terminal to terminal (note that , may or may not equal , depending on the presence of a magnetic ...
Electrical resistivity is obtained from the equation: [1] =, R is the electrical resistance of the specimen, the ratio of voltage to current (measured in ohms, Ω) is the length of the piece of material (measured in metres, m)
Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it can move away by an electric current or electrical discharge. The word "static" is used to differentiate it from current electricity, where an electric charge flows through an electrical conductor. [1]
All devices and connections have non-zero resistance and reactance, and therefore no device can be a perfect source. The output impedance is often used to model the source's response to current flow. Some portion of the device's measured output impedance may not physically exist within the device; some are artifacts that are due to the chemical ...