Phase qubit

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Barlow's law was an incorrect physical law proposed by Peter Barlow in 1825 to describe the ability of wires to conduct electricity.[1][2] It said that the strength of the effect of electricity passing through a wire varies inversely with the square root of its length and directly with the square root of its cross-sectional area, or, in modern terminology:

IAL

where I is electric current, A is the cross-sectional area of the wire, and L is the length of the wire. Barlow formulated his law in terms of the diameter d of a cylindrical wire. Since A is proportional to the square of d the law becomes IdL for cylindrical wires.[2]

Barlow undertook his experiments with the aim of determining whether long-distance telegraphy was feasible, and believed he proved that it was not.[1] Importantly, Barlow failed to recognize the dependence of the current strength on electric tension (that is, voltage) so neglected the possibility of solutions such as a high-intensity battery or step-up voltage converters to allow long-distance telegraphy. The publication of Barlow's law delayed research into telegraphy for several years, until 1831, when Joseph Henry and Philip Ten Eyck constructed a circuit 1,060 feet long, which used a large battery to activate an electromagnet.[3]

In 1827, Georg Ohm published a different law, stating that the current varies inversely with the wire's length, not its square root and varies directly with voltage (V); that is, IALV. Experiments by a variety of scientists proved Ohm's law correct and Barlow's false.

References

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