Choke Coil Definition and Properties - JEE Important Topic

A Brief Introduction to Choke Coil 

In Physics, there are many electronic devices like resistors, capacitors, and inductors which have many applications in our lives. Each device has its own properties, uses, and applications. There is an inductor that we use to resist very high-frequency alternating currents (AC) while only allowing direct currents and lower frequency AC currents to pass through it freely. This is known as a choke and it is made up of coils so it is often termed a choke coil. 

Let us discuss the choke coil construction and the types of choke coil. 

Construction of a Choke Coil

A choke coil has a very small resistance because it is only used to block higher frequency AC currents in a circuit. We can also use a resistor in place of this but due if we use a resistor, there is a lot of energy or power dissipated in the circuit by the usage of a resistor. This is why an inductor is used where there would be no power dissipation at all. Choke means blocking something and preventing its passage. 

To prevent the higher frequency currents, the impedance of the choke coil is set in such a way that the impedance increases with the frequency. This is how it will be able to restrain the amount of the AC current that passes through it. It is often called an inductor rather than a choke coil when used in any electronic filter. The construction of a choke coil is made accordingly to prevent high-frequency alternating currents which is the requirement when it comes to filtering methods and applications. The figure given below is the choke coil diagram which clearly shows what the choke coil in a circuit looks like.  

Choke Coil

As we can see in the image, numerous copper wire turns are present which are insulated and bound to a soft iron core. 

Working of a Choke Coil

Coil of Choke in a circuit

The working of a choke coil is very simple as the working of an inductor. It basically restrains the rate of change in the current in a circuit. The current is initially drawn to zero with the help of bimetallic plates present in the starter. This is the choke inductor in a circuit that provides the voltage in order to let the conduction start in the circuit. 

Now, let’s understand how choke coils are divided into different types and what are their different properties.

Types of a Choke Coil 

Choke coils are divided into two types based on the type of frequency they are supposed to resist and not allow to pass through them. They  are:

• Audio Frequency choke inductor 

• Radio frequency choke inductor 

Let's dive into each one of the types in detail. 

1. Audio frequency Choke Inductor

In this type of choke coil, the core is made up of iron that acts as a magnet and increases the inductance of the coil. These are constructed in such a way that they block audio and power line frequencies and allow direct currents to pass through them. These are widely used in DC motor controllers where the direct current is produced and the AC voltage ripple frequency is not allowed to pass through along with the DC current output. 

In rectifiers, where the AC current is converted, rectified, and filtered into DC current, this choke inductor is also used. If this inductor is removed, then there will be excess and unwanted ripple frequencies of AC current at the DC output. These choke coils range from the smaller chokes which are used in power supply control to the heavy and bulky chokes in frequency power supplies. In some devices like amplifiers and radio receivers, the design of the audio frequency choke is widely used.

2. Radio Frequency Choke Inductor 

Radiofrequency chokes have a core and copper windings winded around the core. Here the core is made up of iron to increase the inductance according to the frequency and for the efficient working of the choke coil. The construction of this choke coil is made very complex in order to reduce many effects on the choke coil. The function of the choke coil used in this type is to resist the radio frequencies and allow the audio frequency and direct currents to pass through it. This is a novel form in the choke coils which is invented to reduce the radio frequency noises in the core. These are often used in wires of electronic devices in our daily life. 

Application of Choke Coil 

There are various applications of choke coils in physics and electronics such as: 

• Choke coils are used in car audio systems to prevent the high audio frequency signals from the amplifier.

• It also has a wide range of uses in computer cables, radio receivers, and amplifiers.

• In tuned circuits and filters, the choke coils are used to block the various high-frequency signals from the AC currents. 

Conclusion  

So here, we discussed topics such as what is choke coil and the uses of a choke coil and got an idea of why it is termed a choke inductor with the help of a choke coil diagram and its construction. By reading this article, one can understand the importance of the choke coil and its prominent uses in electronic circuits. Owing to the highly useful function of choke coils, there are various uses of choke coils that we benefit from in our day-to-day life.