Dielectrics and Insulators

### Insulator

1. **High Resistivity:** Insulators are characterized by their high resistivity, preventing the free flow of electric current.

2. **Large Band Gap:** These materials typically have a large band gap, which keeps electrons in the valence band and prevents electrical conductivity.

3. **Examples:** Common examples include porcelain, rubber, and glass.

4. **Time-Reversal Symmetry:** Certain types, like topological insulators, have surface states protected by time-reversal symmetry.

5. **Mott Insulators:** Predicted by the Hubbard model due to antiferromagnetic order.

6. **Breakdown Voltage:** Insulators can break down at high voltages, allowing current to flow.

7. **Dielectric Use:** They can be used as dielectrics in capacitors, enhancing capacitance.

### Dielectric

1. **Polarizability:** Dielectrics can be polarized by an electric field, leading to increased capacitance in capacitors.

2. **Capacitance Increase:** Placing a dielectric material between capacitor plates increases the capacitance.

3. **Relative Permittivity:** Also known as the dielectric constant, it measures a material's ability to store electrical energy in an electric field.

4. **High Band Gap:** Similar to insulators, dielectrics have a large band gap.

5. **Breakdown Voltage:** Dielectrics have a characteristic breakdown voltage beyond which they conduct electricity.

6. **Common Examples:** Materials such as rubber, plastic, and polystyrene are often used as dielectrics.

7. **Paschen's Law:** In gases, Paschen's law describes the breakdown voltage depending on pressure and gap distance.

These clues are frequently mentioned in academic quiz questions about these materials and highlight their fundamental properties and uses.