JEE Main & Advanced Physics Alternating Current / प्रत्यावर्ती धारा Choke Coil

Choke coil (or ballast) is a device having high inductance and negligible resistance. It is used to control current in ac circuits and is used in fluorescent tubes. The power loss in a circuit containing choke coil is least.

(1) It consist of a Cu coil wound over a soft iron laminated core.

(2) Thick Cu wire is used to reduce the resistance (R) of the circuit.

(3) Soft iron is used to improve inductance (L) of the circuit.

(4) The inductive reactance or effective opposition of the choke coil is given by \[{{X}_{L}}=\omega L=2\pi vL\]

(5) For an ideal choke coil \[r=0,\] no electric energy is wasted i.e. average power \[P=0\].

(6) In actual practice choke coil is equivalent to a \[R-L\] circuit.

(7) Choke coil for different frequencies are made by using different substances in their core.

For low frequency L should be large thus iron core choke coil is used. For high frequency ac circuit, L should be small, so air cored choke coil is used.