Superconductors are useful in a vast number of different technical, mechanical, and scientific applications. For instance, superconductor technologies are under development that could substantially improve the safety and efficiency of the electrical grid. Other technologies allow for new uses of electromagnetism. Computers can benefit from superconductor technologies as well, and some types of scientific instrumentation also make use of the unique electrical properties of superconductors.
The key advantage to superconductors is their ability to transmit an electrical current with next to no resistance. Early superconductors functioned only at extraordinarily low temperatures and were impractical for most applications, as the liquid helium needed to cool them was prohibitively expensive and difficult to work with. Newer, high temperature superconductor technologies make use of materials that have superconductive properties when cooled to temperatures that can be sustained in the much less expensive and more manageable liquid nitrogen.
Perfect transmission of electricity has many applications for the power grid. Technologies that use superconductors in place of much larger semiconductors allow for power to be transmitted using much smaller wires. Additionally, since almost no energy is lost, these systems are far more efficient, meaning that less generating power is needed. Superconductors can also be used to mitigate sudden current spikes in a power grid, which would otherwise cause damage.
Superconductors make extremely efficient electromagnets. This allows for very precise imaging, which is helpful for doctors in need of detailed scans of their patients. It is also useful for the military, where superconducting technologies are used to detect mines and other dangers. Larger superconducting electromagnets allow for magnetic levitation, which is already in use in some high-speed trains.
A new generation of computers will eventually make use of superconductor technologies. The electrical properties of semiconductors impose limits on the amount of computing power that can be built into a conventional microchip. Scientists can get around these limitations and create much faster and more tightly-packed circuits by taking advantage of some of the quantum properties of superconducting materials. Superconductors are also more efficient in their use of power, nearly eliminating the problem of waste heat.
Electrical resistance can make it difficult to design very sensitive instruments. Detection instruments that make use of superconductor technologies are free from this problem. Superconductors do not hinder the flow of even very weak electrical currents, and those very weak currents can be used to create detectors that are capable of picking up extremely faint signals.