• noun the central part of a nuclear reactor, where the fuel rods are sited
  • The central region of a star, planet or other body. In stars the core is the region where temperature and pressure are high enough to support fusion, containing half or more of its mass in a few per cent of the volume. The Earth’s core is a molten zone containing large amounts of iron, whose convection is the cause of the Earth’s magnetism, although there seems to be a small solid inner core at the very centre.
  • A form around which a coil or winding is wound. For example, a ferromagnetic core.
  • A magnetic material, such as iron, around which a magnetic coil is wound. Such a core may be used in a device such as an electromagnet or transformer, and increases the inductance of the coil. Also called magnetic core (1).
  • The center conductor of a coaxial cable, or the bundled optical fibers encased by a protective sheath in a fiber-optic cable. Also called fiber core, or optical fiber core.

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