This is a qualitative difference, not just quantitative. A normal conductor like copper has very low but non-zero resistance — even at 0°C, copper still resists current, converting electrical energy to heat. If you set a current flowing in a copper loop with no EMF, it decays to zero within microseconds due to resistance. A superconductor below Tc has exactly zero resistance — not approximately zero, but mathematically zero. A current set flowing in a superconducting loop can persist for years or even centuries without any power source or measurable decay. This has been experimentally demonstrated. The reason is quantum mechanical: Cooper pairs form a macroscopic quantum state (like a Bose-Einstein condensate) that cannot be gradually slowed down — any perturbation would have to destroy the entire coherent quantum state simultaneously, which has zero probability below Tc. Practical implication: MRI machines have a superconducting loop carrying ~200 amperes of current with zero power consumption to maintain it (once cooled).

Current superconductors require cooling to cryogenic temperatures (77–4 K), which requires expensive liquid nitrogen or helium and complex insulation systems. A room-temperature superconductor (working at 20–30°C) would be transformative: Power transmission: About 7–10% of electricity is lost as heat in transmission lines. Zero-resistance power lines would save trillions of dollars globally and make renewable energy far more viable. Computing: Superconducting quantum computers wouldn't need massive cooling infrastructure — making quantum computing accessible everywhere. Transport: Maglev technology could be deployed cheaply across nations. Energy storage: SMES systems could store energy from renewable sources without loss, solving the intermittency problem. Scientific instruments: Ultra-sensitive magnetic sensors and detectors would transform medicine and geology. The LK-99 episode (2023) shows how desperate the scientific community is for this breakthrough — and why any claim generates immediate global excitement.

A perfect diamagnet would simply prevent magnetic field from entering when it's in the diamagnetic state — it wouldn't actively expel a field that was already present. The Meissner Effect goes further: if you cool a material in the presence of a magnetic field, as it transitions to the superconducting state, it actively expels the field that was already inside it. This means the superconducting state itself — not the path of getting there — determines the magnetic state inside. This is a thermodynamic equilibrium state, not just an inertial effect. For UPSC: This distinguishes a true superconductor (which always expels fields regardless of how it was cooled) from a hypothetical perfect conductor (which would only expel fields that tried to enter after it became perfect). The Meissner Effect is the definitive experimental proof of the superconducting state.

Superconductors connect to India's strategic interests across multiple dimensions: Energy security: Zero-loss power cables would reduce India's massive transmission losses (estimated ~20% in some states). Healthcare sovereignty: Domestic MRI magnet production (achieved) reduces dependence on imports; MRI machines cost ₹3–10 crore, partly due to superconducting magnets. Nuclear energy: India's thorium-based fusion ambitions (SST at IPR Gandhinagar) require mastery of superconducting coil technology. Quantum technology leadership: The National Quantum Mission (₹6,003 crore) includes superconducting qubit development — crucial for cryptography, defence, and computing supremacy. CERN collaboration: India's PIP-II involvement builds cutting-edge superconducting magnet design capability with global implications. Defence: Railguns, EMP shielding, and degaussing are all superconductor-enabled defence technologies. UPSC Mains angle: Superconductors sit at the intersection of energy security, Atmanirbhar Bharat, quantum technology, and scientific leadership — making them extremely relevant for GS-III essays and answers.