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Superconductors
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Materials with zero resistance below a critical temperature.
Below a critical temperature some materials have exactly zero resistance and expel magnetic fields (Meissner effect). Used in MRI magnets and maglev trains.
Mercury at 4.2 K; cuprates up to 138 K.
Not just very low resistance but zero.
In more detail
Superconductors have zero electrical resistance below a critical temperature. Currents can flow indefinitely without loss, and they expel magnetic fields.
Real-world uses
- MRI magnets use superconducting coils to produce strong fields.
- Particle accelerators use superconducting magnets.
- Superconducting magnets in MRI scanners carry large currents with no resistance, which saves energy and allows strong fields.
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Frequently asked questions
Are superconductors room temperature?
Most known superconductors need very low temperatures, though research continues.
Why is there no resistance?
Electrons form pairs that move without scattering in the lattice.
Do superconductors need extreme cold?
Conventional superconductors need very low temperatures, while newer materials superconduct at higher temperatures, though still far below room temperature.
Related topics in Current Electricity & Circuits
Resistivity · Conductivity · Temperature dependence of resistance · Semiconductors and thermistors · Resistors in series · Resistors in parallel