Magnetic resonance systems receive coils

These systems work by placing a sample between the pole pieces of a magnet (electromagnet or permanent), surrounded by a coil of wire. Radio frequency (r.f.) is fed into the wire at a swept set of frequencies. Alternatively, the magnet may have extra coils built onto the pole pieces which can be used to sweep the field with a fixed r.f. When the combination of field and frequency match the resonant frequency of each nucleus r.f. is emitted and captured by a receiver coil perpendicular to the transmitter... 

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