Electric guitar
Pickups

Compared to an acoustic guitar, which has a hollow body, electric guitars make much less audible sound when their strings are plucked, so electric guitars are normally plugged into a guitar amplifier and speaker. When an electric guitar is played, string movement produces a signal by generating (i.e., inducing) a small electric current in the magnetic pickups, which are magnets wound with coils of very fine wire.The signal passes through the tone and volume circuits to the output jack, and through a cable to an amplifier. The current induced is proportional to such factors as string density and the amount of movement over the pickups.

Because of their natural qualities, magnetic pickups tend to pick up ambient, usually unwanted electromagnetic interference or EMI. This mains hum results in a tone of 50 or 60 cycles per second depending on the powerline frequency of the local alternating current supply.

The resulting hum is particularly strong with single-coil pickups. Double-coil or " humbucker " pickups were invented as a way to reduce or counter the sound, as they are designed to "buck" (in the verb sense of oppose or resist) the hum, hence their name. The high combined inductance of the two coils also leads to the richer, "fatter" tone associated with humbucking pickups.
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