Definition
The energy lost as heat in an insulating material (a dielectric) when it is subjected to a changing electric field, such as the field between the plates of a capacitor carrying alternating current. The insulator's molecules cannot follow the field changes perfectly, and the resulting internal friction converts a small portion of the electrical energy into heat.
Plain English
When an insulator sits between two electrical conductors and the voltage keeps changing, a tiny amount of electrical energy turns into heat inside the insulator instead of doing useful work. That wasted energy is the dielectric loss.
Context Anchor
Seen in aircraft electrical and radio equipment discussions, especially where insulation, capacitors, antenna cables, or high-frequency signals are involved.
Derivation
Dielectric comes from the Greek 'dia' (through) and the English 'electric.' It describes a material that an electric field passes through but electric current does not. 'Loss' simply means energy that doesn't make it out the other side. Together: energy lost while passing an electric field through an insulator.
Why Pilots Care
Excessive dielectric loss in capacitors or wiring insulation can produce heat, reduce efficiency, and shorten the life of avionics and electrical components.
Grounding Statement
In a fast-changing electrical field, the insulating material can absorb a small amount of energy and warm up.
Intuition Check
Dielectric loss does not mean the insulation has completely failed or that there is a direct short. It means some energy is being absorbed by the insulating material and turned into heat.
Example Sentence 1
The capacitor was warm to the touch after extended operation, a normal sign of dielectric loss at high frequencies.
Example Sentence 2
High dielectric loss in the coaxial cable insulation caused the transmitter to run hotter than normal.