Constantan Resistance Wire for Laboratory Electrical Experiments

Description

The Constantan Resistance Wire, also known as Eureka resistance wire, copper-nickel resistance wire or laboratory Constantan wire, is designed for investigating electrical resistance, conductor properties and the relationship between electricity and temperature in laboratory environments. Manufactured from a copper-nickel alloy, this resistance wire is identified in the supplied product information as approximately 60% copper and 40% nickel. Constantan is valued for its relatively high electrical resistivity and low temperature coefficient of resistance compared with ordinary copper conductors.

The range includes ten Standard Wire Gauge (SWG) sizes, from 18 SWG to 36 SWG, allowing laboratories to select different conductor thicknesses for electrical resistance experiments and educational demonstrations. The 18 SWG Constantan Wire has a nominal diameter of 1.22 mm, with supplied reference values of 0.42 Ω/m electrical resistance and 10.384 g/m mass. These figures relate to the 18 SWG specification and should not be applied to the other wire gauges. The 20 SWG, 22 SWG and 24 SWG variations have standard nominal diameters of approximately 0.91 mm, 0.71 mm and 0.56 mm, respectively. These sizes are useful for comparing resistance in conductors with different cross-sectional areas. The 26 SWG, 28 SWG, 30 SWG and 32 SWG wires provide progressively finer conductor options for laboratory circuit construction and resistance measurements. Their smaller diameters generally produce greater resistance per metre than thicker Constantan wire of the same alloy. The finer 34 SWG and 36 SWG variations are suitable for experiments requiring smaller conductor diameters. The supplied 34 SWG diameter is approximately 0.23 mm, while the 36 SWG diameter requires confirmation because the listed 0.22 mm differs from the standard nominal SWG value.

One important characteristic of Constantan is its low temperature coefficient of resistance. Unlike many conventional metallic conductors, Constantan exhibits comparatively small resistance changes over a suitable temperature range. Its resistance is not completely independent of temperature, and actual behaviour depends on the alloy composition. This characteristic makes Constantan wire useful in electrical resistance experiments, precision resistance demonstrations and Wheatstone bridge circuits, where variations in conductor resistance can affect measurement results. Students can also use Constantan wire to investigate Ohm’s law, measuring voltage and current through a known wire length to determine electrical resistance.

Different wire gauges support investigations of the relationship between conductor length, diameter and resistance. For a uniform wire of the same alloy at a fixed temperature, resistance increases with length and decreases as cross-sectional area increases. Constantan wire may also be used in resistance coils and experimental electrical assemblies. Because the supplied wire is bare, adjacent turns can make electrical contact, so electrical separation must be provided where required. The wire is identified by several related commercial names, including Constantan, Eureka, Advance and Ferry. However, alloy compositions can vary between manufacturers, so the exact grade should be confirmed where electrical performance or temperature stability is critical.

Safety Precautions: Use suitable low-voltage, current-limited power supplies during laboratory experiments. Bare Constantan wire is electrically conductive and can become hot when current passes through it. Avoid contact with energised conductors and do not use exposed resistance wire directly with mains electricity. These products are intended for laboratory and educational settings only and should be used under appropriate supervision. Each selected variation is listed as one 125 g Reel of Constantan (Eureka) Resistance Wire in the chosen SWG size. The repeated supplier descriptions also refer to 50 g reels, so the final packaging weight should be confirmed before ordering or publication.

LabChoice Australia supplies Constantan resistance wire, electrical conductors and educational physics equipment for secondary schools, universities, research institutions, electrical science laboratories and educational facilities across Australia.