Conduction in Solids

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Conductor Noun

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[kon-duk-ter]

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Conductor

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A material where electric charges move easily due to partially filled or overlapping energy bands, allowing for current flow.

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Example: This image shows a penny completing an electrical circuit, causing a bulb to light up. This demonstrates that the metal penny is a conductor.

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Insulator Noun

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[in-suh-ley-ter]

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Insulator

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A material that resists the flow of electric charge because of a large energy gap between its valence and conduction bands.

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Example: This image shows examples of electrical insulators like rubber, glass, and wood, which are materials that do not allow electricity to pass through them easily.

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Semiconductor Noun

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[sem-ee-kon-duk-ter]

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Semiconductor

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A material with electrical conductivity between that of a conductor and an insulator, featuring a small, non-zero energy gap.

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Example: This diagram shows how adding specific impurities to a semiconductor material (like silicon) changes its ability to conduct electricity by creating either extra electrons or 'holes'.

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Valence Band Noun

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[vey-luhns band]

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Valence Band

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The lower range of electron energy levels in a solid, which is typically filled with the bonding electrons of the crystal.

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Example: This diagram shows the valence band as the lower energy level in a semiconductor, separated from the conduction band by an energy gap.

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Conduction Band Noun

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[kon-duk-shun band]

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Conduction Band

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The higher range of electron energy levels in a solid, where electrons can move freely between atoms to conduct electricity.

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Example: This diagram shows the conduction band, an energy level where electrons can move freely to conduct electricity, and its separation from the lower valence band.

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Energy Gap Noun

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[en-er-jee gap]

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Energy Gap

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A forbidden range of energy levels that electrons cannot occupy, located between the valence and conduction bands in solids.

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Example: This diagram shows the energy gap, a 'forbidden' zone that electrons must jump from the valence band to the conduction band for electricity to flow.

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Conductivity Noun

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[kon-duk-tiv-i-tee]

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Conductivity

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A fundamental property of a material measuring its ability to conduct electric current; it is the reciprocal of resistivity.

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Example: This diagram shows that heat energy naturally flows from a hotter object to a colder object, which is the principle of thermal conduction.

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Resistivity Noun

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[ree-zis-tiv-i-tee]

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Resistivity

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A fundamental property of a material that quantifies its opposition to the flow of electric current; the reciprocal of conductivity.

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Example: This diagram shows that a material's resistivity (ρ), along with its length (L) and cross-sectional area (A), determines its total electrical resistance (R).

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Electric Conduction Noun

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[ih-lek-trik kon-duk-shun]

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Electric Conduction

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The process of electric current flow, which involves the movement of charged particles, such as electrons, through a material.

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Example: This image shows that without voltage, free electrons in a solid conductor move randomly. When voltage is applied, they flow in a single direction, creating an electric current.

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Intrinsic Semiconductor Noun

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[in-trin-zik sem-ee-kon-duk-ter]

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Intrinsic Semiconductor

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A pure semiconductor whose electrical conductivity is a natural property of the material itself, without any added impurities or dopants.

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Example: This diagram shows a pure silicon crystal where thermal energy has freed an electron, creating a mobile 'free electron' and a 'hole' for conduction.