Magnetic field and Skin Effect

[rapids79]

I have been trying to understand the field theory from the basics and have come across a few things I have not understood a few things clearly:

1. The magnetic field strength is maximum at the center of the conductor and decreases with an increase in the distance from the center. I understand this mathematically, i.e. the field strength is inversely proportional to the distance as per the mathematical relation, but I don't understand the physics behind it.

2. In the book "RF Circuit Design" by Chris Bowick, he says that "As the frequency is increased, an increased magnetic field at the center of a conductor presents increased impedance to the charge carriers, thus decreasing the current density at the center of the conductor and increasing the current density around it perimeter." My question is, why would an increased magnetic field strength provide impedance to the movement of charge carriers as it does at the center of the conductor.

I'd be grateful if someone could throw some light on this. Thanks.

 

[eljose79]

I can provide some clarification on these concepts for you.

1. The reason why the magnetic field strength is maximum at the center of a conductor is due to the principle of superposition. This principle states that the total magnetic field at any point is equal to the vector sum of the individual magnetic fields produced by each current element in the conductor. At the center of the conductor, the magnetic fields produced by each current element are in the same direction and add up, resulting in a stronger magnetic field. As you move away from the center, the magnetic fields produced by the current elements start to cancel out, resulting in a decrease in overall magnetic field strength.

2. In the case of an increasing frequency, the magnetic field strength at the center of the conductor increases. This increase in magnetic field strength creates a greater opposition to the movement of charge carriers, known as impedance. This is because the charge carriers experience a greater force from the magnetic field, making it more difficult for them to move through the conductor. As a result, the current density at the center of the conductor decreases, while the current density around the perimeter increases. This is known as skin effect and is a common phenomenon in high frequency circuits.

I hope this helps to clarify the physics behind these concepts. If you have any further questions, please don't hesitate to ask. Keep up the curiosity and keep learning!