Search results
Results From The WOW.Com Content Network
Also called chordal or DC resistance This corresponds to the usual definition of resistance; the voltage divided by the current R s t a t i c = V I. {\displaystyle R_{\mathrm {static} }={V \over I}.} It is the slope of the line (chord) from the origin through the point on the curve. Static resistance determines the power dissipation in an electrical component. Points on the current–voltage ...
Original data from the 1911 experiment by Heike Kamerlingh Onnes showing the resistance of a mercury wire as a function of temperature. The abrupt drop in resistance is the superconducting transition. The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered.
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.
Joule immersed a length of wire in a fixed mass of water and measured the temperature rise due to a known current flowing through the wire for a 30 minute period. By varying the current and the length of the wire he deduced that the heat produced was proportional to the square of the current multiplied by the electrical resistance of the ...
A convenient formula (attributed to F.E. Terman) for the diameter D W of a wire of circular cross-section whose resistance will increase by 10% at frequency f is: [7] = / This formula for the increase in AC resistance is accurate only for an isolated wire.
Parasitic resistance is a more general term, of which it is usually assumed that contact resistance is a major component. William Shockley [ 1 ] introduced the idea of a potential drop on an injection electrode to explain the difference between experimental results and the model of gradual channel approximation.
Nichrome, a non-magnetic 80/20 alloy of nickel and chromium, is the most common resistance wire for heating purposes because it has a high resistivity and resistance to oxidation at high temperatures, up to 1,400 °C (2,550 °F). When used as a heating element, resistance wire is usually wound into coils.
Introducing the constant of proportionality, the resistance, [14] one arrives at the usual mathematical equation that describes this relationship: [15] =, where I is the current through the conductor in units of amperes , V is the potential difference measured across the conductor in units of volts , and R is the resistance of the conductor in ...