Branch of Electricity: Electronics
- Deals with components that use small currents, such as semiconductors, capacitors, thermostats, diodes, and transistors.
Band Theory
- Explains how energy levels in atoms form energy bands in solids, including conductors, semiconductors, and insulators.
Energy Levels
- Shells of an atom are called energy levels because they represent different amounts of energy.
Valence Band
- The outermost shell of an atom where electrons reside. This band may not always be completely full.
Conduction Band
- An imaginary band outside the valence band where free electrons can move after gaining energy from the valence band.
Forbidden Gap
- The energy gap between the valence band and conduction band, where no electron can exist.
Conductors
- In metals, the valence band is close to the conduction band, with a narrow forbidden gap, requiring little energy for electrons to move, allowing current flow easily.
Semiconductors
- Materials like silicon, boron, and germanium that can conduct electricity under certain conditions.
- Act as insulators at very low temperatures but become poor conductors at room temperature.
- Have a relatively narrow forbidden gap, requiring less energy to move electrons from the valence to conduction band.