Electric Field and Dielectric

In this section, the speaker explains how electric fields affect dielectrics. The speaker describes dipoles and how they are affected by external fields. They also explain how the total field is calculated and how it changes with the dielectric constant.

Dielectric Dipoles

• Electrons in atoms stretch to form dipoles when exposed to an electric field.

• Positive and negative charges in a dielectric neutralize each other, but an external field causes two sheets of bound charge to form on top and bottom.

• Two sheets of charge create their own field, which adds up with the external field to give the total field.

Total Field Inside a Dielectric

• The total field inside a dielectric is equal to the external field times one minus M constant divided by epsilon (the dielectric constant).

• The M constant is inversely proportional to epsilon R (relative permittivity), so as epsilon R increases, the total field decreases.

• A higher epsilon means a lower total field inside.

Dielectric Strength

• The strength of a dielectric refers to how much voltage can be applied per meter before it breaks down.

• Air can handle 3 MW/m while mylar can handle 200 MV/m before breaking down.

• When voltage exceeds this limit, electrons that are normally tightly bound will start being pulled out of atoms, causing conduction current flow.

Tangent Delta and Leakage Current

In this section, the speaker discusses tangent delta and its relationship with leakage current. They explain how epsilon R double prime (the imaginary part of the dielectric constant) is represented in data sheets as tangent delta.

Tangent Delta

• Epsilon R double prime is the imaginary part of the dielectric constant and is represented in data sheets as tangent delta.

• Tangent delta describes the actual conduction current that will flow through a dielectric.

• Tangent delta is calculated by dividing epsilon R double prime by epsilon R prime.

Leakage Current

• Epsilon R prime represents an ideal dielectric, while epsilon R double prime describes leakage current.

• Leakage current refers to the actual conduction current that flows through a dielectric.