• summary_type: application
• word_count: 140

A choke coil is a high-inductance, low-resistance inductor used to limit AC current without significant power loss. In a series circuit, the choke provides impedance X_L = omega*L, reducing the current to I = V/sqrt(R^2 + X_L^2) without the I^2R losses that a series resistor would cause. The power factor cos(phi) = R/sqrt(R^2 + X_L^2) is small, meaning most of the circuit's apparent power is reactive (stored and returned, not dissipated). Practical use: in fluorescent lamp circuits, the choke limits current through the tube. An iron-core choke (low frequency, 50 Hz) is used for mains applications; an air-core choke (high frequency, RF) is used in radio circuits. The iron core increases inductance but introduces some hysteresis and eddy current losses.