Choke coil – principle, working, and construction, class 12

Knowledge Increases By Sharing...

In this article, we will discuss the Choke coil – principle, working, and construction, so let’s get started…

What is a Choke coil?

What is a Choke coil?
Choke coil

A choke coil is simply an inductor with large inductance that is used to reduce the current in a.c. circuits without much loss of energy.

Principle of a choke coil

The working of a choke is based on the fact that when a.c. flows through an inductor, current lags behind the emf by a phase angle of $\pi / 2 \mathrm \;{rad}$.

Construction of a choke coil

It is made of thick insulated copper wire wound closely in a large number of turns over a soft-iron laminated core. Choke coil offers a large reactance $X_L=2 \pi f L$ to the flow of a.c. and hence current is reduced. A laminated core reduces losses due to eddy currents.

Read Also

Working of a choke coil

As shown in the Figure below, a choke is put in series across an electrical appliance of resistance $R$ and is connected to an a.c. source. This forms an $L R$-circuit.

Choke coil - principle, working, and construction, class 12

The average power dissipated per cycle in the circuit is –

$$P_{a v}=V_{eff} I_{eff} \cos \phi=V_{eff} I_{eff} \cdot \frac{R}{\sqrt{R^2+\omega^2 L^2}}$$

Inductance $L$ of the choke coil is very large so that $R<<\omega L$. Then
Power factor, $\cos \phi \simeq \frac{R}{\omega L} \simeq 0$
i.e. the Average power dissipated by the coil is very small. As $Z=\sqrt{R^2+\omega^2 L^2}$ is large, so current is reduced without appreciable wastage of power.

Preference of choke coil over the ohmic resistance

A choke coil reduces the current in a.c. circuit without consuming any power. When an ohmic resistance is used, current reduces but energy losses occur due to heating. So a choke coil is preferred.

Application of choke coil

The most common use of choke coil is in fluorescent tubes with a.c. mains. If the tube is connected directly across $220 \mathrm{~V}$ source, it would draw large currents which would damage the tube.

With the use of a choke coil, the voltage is reduced to an appropriate value, without wasting any power. Choke coils are also used in various electronic circuits, mercury lamps, and in sodium vapor lamps.

Read Also

Stay tuned with Laws Of Nature for more useful interesting content.

Was this article helpful?
Knowledge Increases By Sharing...

Newsletter Updates

Enter your email address below and subscribe to our newsletter

0 0 votes
Rate this Article
Notify of

Inline Feedbacks
View all comments
Would love your thoughts, please comment.x