In a superconductor, the electric resistance is equal to zero. This is why an electric current can circulate forever in a superconducting ring even when the battery has been unplugged! This is how magnetic fields are created in MRIs. It might seem odd that a battery could create a low voltage electric current at the terminals of a superconducting network, since the voltage should be equal to zero because of the absence of electric resistance. What happens is that the electric tension created by the battery is divided into the other parts of the network, i.e. the metallic wires that link the battery to the superconductor and to the interior of the battery (internal resistance).

Superconductors have almost zero resistance.

Explanation:
- Superconductors are a special class of materials that exhibit zero electrical resistance when cooled below a certain critical temperature.
- At temperatures above the critical temperature, superconductors behave like regular conductors, but as the temperature decreases, their resistance drops rapidly until it reaches zero.
- This phenomenon is known as superconductivity and is characterized by the expulsion of magnetic fields, a property called the Meissner effect.
- Superconductors can carry electric currents without any loss of energy due to resistance, making them extremely useful in various applications, such as power transmission, magnetic levitation, and high-speed computing.
- The critical temperature at which superconductivity occurs varies for different materials. Some superconductors require extremely low temperatures, close to absolute zero (-273.15°C), while others can exhibit superconductivity at relatively higher temperatures, known as high-temperature superconductors (HTS).
- The discovery of superconductivity has revolutionized the field of electrical engineering, as it allows for the efficient transmission of electricity and the development of powerful electromagnets.
- Superconductors are typically made from certain metals, alloys, or compounds, such as niobium-titanium, niobium-tin, and yttrium-barium-copper oxide (YBCO).
- The zero resistance property of superconductors is due to the formation of Cooper pairs, which are pairs of electrons that overcome their natural repulsion and form a bound state with zero net electrical charge.
- The flow of electric current in a superconductor is carried by these Cooper pairs, and since there is no resistance, the current can circulate indefinitely without any energy loss.

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