CA choke coil is an electrical appliance used for controlling current in an circuit. If we use a resistance R for the same purpose, a lot of energy would be wasted in the form of heat etc.
The choke coil consists of a number of urns of thick copper wire wound closely over a /laminated soft iron core. The inductive reactance offered by the coil XL = w L is large. Therefore magnitude of a.c is reduced since
Iu = Eu / XL
In an ideal choke coil, ohmic resistance = 0 therefore there is no energy dissipation. Through an ideal inductor current lags behind the applied voltage by a phase angle of 90.
∴ Average power consumed by the choke coil over a complete cycle is
P = E0 I cos ∅ = E I cos 90 = 0
However in actual practice a choke coil of inductance L is having a small resistance r it may be treated as a series combination of L and r. therefore average power consumed over a complete cycle in the practical choke coil is
P = E I cos ∅
P = E I r / r2 + w2 L2
This comes out to be much smaller than the power loss (i2 R) if a resistance R is used for reducing a.c.
For reducing low frequency alternating current choke coils with laminated soft iron cores are used.
This is because I = Eu / XL = Eu / wL = Eu / 2 π vL
When v is low L is made high using soft iron core.
These are called the chokes represented in fig. 1
For reducing high frequency alternating currents air cored chokes are used.
I = E0 / XL = Eu / wL = Eu / 2π v L
When v is high L need not be made high air cored chokes are used.
These are called the chokes represented in fig .2
We have seen the use of choke coil in series with a fluorescent tube working on A.C mains.
Choke Coil Assignment Help, Choke Coil Homework Help, Choke Coil Tutors, Choke Coil Solutions, Choke Coil Tutors, Electrostatics Help, Physics Tutors, Choke Coil Questions Answers