Loss tangent of medium

 

loss tangent  of medium

Loss tangent is the ratio of the magnitude of conduction current density to displacement current density of the medium. 

Loss tangent is a measure of the lossy nature of a medium at a particular frequency.

Loss tangent is given by  

 

 

 

 

 

Skin Effect

 

Skin Effect

 

The electric current flows mainly at the "skin" of the conductor, between the outer

surface and a level called the skin depth. The skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller, thus reducing the effective cross-section of the conductor.

The phenomenon whereby field intensity in a conductor rapidly decreases is known as skin effect.

Skin depth  is defined as that depth in which the wave has been attenuated to 1/e or approximately 37% of its original value. i.e.

 

for any material medium. 

practical significance of skin depth:

Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. At 60 Hz in copper, the skin depth is about 8.5 mm.

 

The skin depth is a measure of the depth to which an EM wave can penetrate the

medium.

skin depth δ For good conductors is given by

                                                                                                                                            

Skin depth in Copper at different frequencies :