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What is superconductivity?

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Quick answer

Superconductivity is a state in which certain materials conduct electricity with exactly zero resistance once cooled below a critical temperature. Current can then flow forever without losing energy, and the material pushes out magnetic fields — the effect behind MRI machines and maglev trains.

Key things to understand

  1. Below a critical temperature, electrical resistance drops to absolute zero — no heat, no energy lost.
  2. Superconductors expel magnetic fields (the Meissner effect), letting magnets levitate above them.
  3. Electrons bind into 'Cooper pairs' that glide through the material without scattering.
  4. Most need extreme cold (near −270°C); 'high-temperature' ones still need around −140°C.
  5. Used in MRI scanners, maglev trains, particle accelerators, and quantum computers.

People also ask

Why does a superconductor have zero resistance?
Its electrons pair up and move in lockstep, so they stop colliding with the atomic lattice and lose no energy as heat.
What is a room-temperature superconductor?
A long-sought material that would superconduct without cooling. It would transform power grids and electronics, but no reliable, reproducible one exists yet.
What is the Meissner effect?
A superconductor pushes magnetic fields out of its interior, which is why a magnet floats steadily above a cooled superconductor.
Why do superconductors need to be so cold?
Heat makes atoms vibrate and disrupt the electron pairing that enables zero resistance; cooling quiets the vibrations so superconductivity can occur.
How do superconductors make things levitate?
They push out magnetic fields, so a magnet placed above one is repelled and floats — the basis of maglev trains.