Dielectric loss, also known as dielectric dissipation factor or loss tangent, refers to the energy loss that occurs in a dielectric material when it is subjected to an alternating electric field. It is a measure of how effectively a dielectric material absorbs and dissipates energy.

Dielectric loss arises from various mechanisms, including molecular dipole rotation, ionic conduction, electronic polarization, and interfacial losses. When an alternating electric field is applied, the energy absorbed by the dielectric material is not completely stored and released back but is partially dissipated as heat due to these mechanisms.

The dielectric loss is quantified by the loss tangent (tan δ), which is the ratio of the imaginary part (ε'') of the complex dielectric constant (ε) to the real part (ε'):

tan δ = ε'' / ε'

The loss tangent provides a measure of the efficiency with which a dielectric material converts electrical energy into heat. A higher loss tangent indicates a higher energy dissipation or greater dielectric loss.

Dielectric loss is an important consideration in many applications of dielectric materials, such as capacitors, insulating materials, and microwave devices. It affects the performance and efficiency of these devices by impacting factors such as power dissipation, signal integrity, and dielectric breakdown. Materials with lower dielectric loss are desirable for applications where energy efficiency and minimal heat generation are crucial.

When an electric field acts on dielectric medium, it absorbs certain amount of energy . This phenomenon loses the energy of the applied field. This loss is commonly known as dielectric loss.

Let's consider alternating electric field

E = Eo cos wt ........1

Case 1: When vector D is in phase with vector E

If vector D is in phase with vector E then

vector D = Pocos wt ....2

So, the current density,

Then the energy loss in time 't' is

We can see that no loss in dielectric medium when vector D is out of phase with vector E.

D = Do cos (wt - δ ) .....4

δ is phase difference between vector D and E.

Average energy loss is

If we suppose applied field is complex i.e E = Eoe^iwt, D is complex.

then obviously the dielectric constant 𝜖* (ratio of D to E) is complex. So

𝜖* = D*/E*

The imaginary part of the complex dielectric constant represents the absorption or dissipation of energy by the medium as a wave propagates through it.

This note is a part of the Physics Repository.

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