Superconductors are used where large currents or zero energy loss are needed

Resistivity & Superconductivity — AQA A-Level Physics

Zero resistanceThe opposition to currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A). flow. The ratio of potential difference to currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A).. Measured in ohms (Ω). means no I²R heating. Superconducting wires can carry enormous currents without energyThe capacity to do work. Measured in joules (J). loss.
Applications that exploit strong magnetic fields (from large currents):
MRI scanners: superconducting coils produce the strong, stable magnetic field needed to image the body.
Particle accelerators: superconducting magnets steer and focus particle beams at near-light speeds.
Maglev trains: superconducting electromagnets levitate the train above the track, eliminating friction. Speeds up to 600 km/h.
Fusion reactors: superconducting magnets confine plasma at millions of kelvin.

Applications that exploit zero energyThe capacity to do work. Measured in joules (J). dissipation:
PowerThe rate of energy transfer. Measured in watts (W). transmission cables: superconducting cables would eliminate the energyThe capacity to do work. Measured in joules (J). lost as heat in conventional copper cables.
Transformers and generators: reduced fire risk and higher efficiencyThe ratio of useful energy output to total energy input, expressed as a fraction or percentage..
Microchips: superconducting interconnects could eliminate resistive heating in processors.

CurrentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A). limitation: maintaining temperatures below T_c requires expensive cryogenic cooling.
Research into high-temperature superconductors aims to raise T_c above liquid nitrogen temperature (77 K) to reduce cooling costs.

Examiner Tips and Tricks

When asked to 'state one use of superconductors', pick one with a clear link to the physics.
MRI scanners need strong magnetic fields, which require large currents, which are only practical with zero-resistanceThe opposition to current flow. The ratio of potential difference to current. Measured in ohms (Ω). wires.
That chain of reasoning is what AQA wants.