# Superconductivity Simulator - Zero Resistance, Meissner Effect, Critical Fields, Levitation

> Resistance drop at T_c for real superconductors, Meissner field lines, type I/II phase diagram and vortex lattice, London depth, flux-pinning levitation, MRI.

- URL: https://qilingtools.com/en/physics/superconductivity
- Category: Physics Tools (https://qilingtools.com/en/physics)
- Tags: [Physics](https://qilingtools.com/en/tags/physics), [Education](https://qilingtools.com/en/tags/education)
- Last updated: 2026-10-29
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

From mercury, lead and niobium to NbTi, Nb₃Sn, MgB₂, YBCO and BSCCO, see resistance drop to zero at the critical temperature and which materials liquid nitrogen can cool. A field-line animation contrasts a superconductor with a hypothetical perfect conductor when the field is applied before cooling, and a draggable B–T phase diagram shows type I and type II behaviour and the Abrikosov vortex lattice. There is also the London penetration depth, frozen-image flux-pinning levitation, and estimates for MRI magnet energy, electrodynamic maglev and persistent-current decay.

## How to use

1. In Resistance drop pick a material, drag the temperature or run a cool-down sweep, then add a field to push T_c down
2. In Meissner effect apply the field, cool below T_c, then switch to the perfect conductor and repeat to compare the field lines
3. In Critical fields & vortices drag the dot on the phase diagram into the mixed state to see vortex spacing and the local field
4. In Flux-pinning levitation set the magnet and cooling gap, drag the magnet and let go, or hang it below the superconductor
5. In MRI · maglev · persistent current enter field, coil size and current to get stored energy and the helium boiled off in a quench

## Features

- Ten superconductors with T_c, critical fields, λ, ξ, κ and discovery year, plus Bloch–Grüneisen normal resistance
- Meissner field-line animation with screening currents, compared with flux freezing in a perfect conductor
- Draggable B–T phase diagram with B_c1 and B_c2 curves and a K₀-based vortex-lattice field map
- London penetration depth λ(T), field decay below the surface, GL parameter κ and type classification
- Field-cooled and zero-field-cooled levitation dynamics from the frozen-image model, force curves and oscillation frequency
- MRI solenoid ampere-turns, inductance, stored energy and quench helium; EDS maglev lift and drag; persistent-current time constant

## FAQ

### How is a superconductor different from a perfect conductor?

A perfect conductor only resists changes of flux: apply a field and then cool it, and the flux is frozen inside. A superconductor actively expels the flux when it is cooled below T_c (the Meissner–Ochsenfeld effect), so the inside is field-free whichever order you choose. That shows superconductivity is a thermodynamic phase, not just very low resistance.

### What separates type I from type II superconductors?

The GL parameter κ = λ/ξ. With κ < 1/√2 (type I) superconductivity is lost all at once above B_c. With κ > 1/√2 (type II) the field enters between B_c1 and B_c2 as quantised vortices, each carrying Φ₀ = h/2e, arranged in a triangular lattice, and the material still has zero resistance. NbTi, Nb₃Sn and the cuprates are type II, with B_c2 from tens to over a hundred tesla.

### Why does a magnet lock in place above a high-temperature superconductor, even upside down?

YBCO is type II, and its flux vortices get pinned by defects. When it is cooled near a magnet, the pinned flux remembers the magnet’s position: push the magnet closer and Meissner repulsion pushes back, pull it away and the pinned flux pulls it back. The frozen-image model treats this as a repulsive image plus an attractive image fixed at the cooling position, so any displacement up or down is restored.

### What happens when an MRI magnet quenches?

A 1.5 T whole-body MRI coil stores more than a megajoule of magnetic energy. If a spot goes normal, resistive heating spreads and the energy turns into heat within seconds, boiling hundreds of litres of liquid helium into about 700 times its volume of gas, so magnet rooms need a quench pipe to vent it outside. In normal use the magnet runs in persistent mode and its current circulates for years with almost no decay.

### Why is liquid nitrogen enough for high-temperature superconductors?

Liquid nitrogen boils at 77 K, costs far less than liquid helium and needs no elaborate recovery system. YBCO (92 K), Bi-2223 (110 K) and mercury cuprates (about 134 K) all have T_c above 77 K and can work immersed in it. NbTi (about 9 K) and Nb₃Sn (18 K) need liquid helium or a cryocooler, and MgB₂ (39 K) can run on liquid hydrogen or a cryocooler.

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