Ohm's Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems.

The relationship between voltage and current is defined (in ohmic devices like resistors) by Ohm's law. Perhaps an inductor could be likened to a fly wheel apparatus. Perhaps a capacitor could be likened to a U bend where a higher water level can store energy and build up a head of pressure. A resistor would be a reduced diameter somewhere in the piping or something akin to a radiator offering resistance to flow. In the water-flow analogy, sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage (difference in electric potential) is likened to difference in water pressure, while current is proportional to the amount of water flowing.

Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc., and no correction terms are required in a practical implementation.

This standard is typically realized using a series-connected array of several thousand or tens of thousands of junctions, excited by microwave signals between 10 and 80 GHz (depending on the array design). As a consequence of the 2019 redefinition of SI base units, as of 2019 the Josephson constant has an exact value of K J = 483 597.848 416 98. GHz/V, which replaced the conventional value K J-90. Historically, the ' conventional' volt, V 90, defined in 1987 by the 18th General Conference on Weights and Measures and in use from 1990 to 2019, was implemented using the Josephson effect for exact frequency-to-voltage conversion, combined with the caesium frequency standard.įor the Josephson constant, K J = 2 e/ h (where e is the elementary charge and h is the Planck constant), a 'conventional' value K J-90 = 0.4835979 GHz/μV was used for the purpose of defining the volt. V = potential energy charge = J C = kg ⋅ m 2 ⋅ s − 2 A ⋅ s. It can be expressed in terms of SI base units ( m, kg, s, and A) as Equivalently, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it. One volt is defined as the electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points.

Microvolts symbol