Question

Explain the term choke coil.

Answer 1

1. If we use a resistance to reduce the current passing through an AC circuit, there will be loss of electric energy in the form of heat (I²RT) due to Joule heating.
2. A choke coil is an inductor, used to reduce AC passing through a circuit without much loss of energy.
3. It is made up of thick insulated copper wires wound closely in a large number of turns over a soft iron laminated core.
4. Choke coil offers large resistance X_L = ωL to the flow of AC and hence current is reduced. Laminated core reduces eddy current loss.
5. Average power dissipated in the choke is P = I_rms E_rms cos Φ , where the power factor, `cos"Φ"  =R/sqrt(R^2+omega^2L^2)`
6. For a choke coil, L is very large. Hence R is very small so cos Φ is nearly zero and power loss is very small.
7. The only loss of energy is due hysteresis loss in the iron core, which can be reduced using a soft iron core.