Electrical Properties

Electrical Conductivity (𝝈)

Definition: The ability/ease of a material to conduct electrical current

Equation: 1 / Ωm or 1 / ρ

• Inverse of resistivity

Electrical Resistivity (ρ)

Definition: Intrinsic resistance of a material to electrical current

Equation: R = ρ (L / A)

Units: Ωm

• Inverse of conductivity

Electrical Resistance (R)

Definition: opposition to electric current through a particluar object

Equation: R = (V / I)

Units: Ω

• Performance Parameter

• Depends on size and geometry

Dielectric Strength

Definition: maximum electric field a material can withstand before electrical breakdown

Equation: E = V / d

Units: V / m

Relative Permittivity / Dielectric Constant (εᵣ)

Definition: Ability of a material to store electrical energy relative to a vacuum

Equation: εᵣ = (ε / ε₀)

Dielectric

Electrical insulating material that can store electrical energy when exposed to an electric field

Capacitor

Small electronic part that stores electrical part that stores electrical energy and releases it quickly

Piezoelectricity

• A cross-property combining both the electrical & mechanical response of a material

• Electrical insulators because they must support an internal applied voltage to function

Piezoelectric Coefficient (dₓₓ)

• Materials constant

• Larger d indicates larger effect

• Direct effect (“piezoelectric”): Q = dF

• Reverse effect (“electrostriction”): S = dE

Band Gap Theory

• The Valence Band (Ground Floor / Home): This is where electrons are comfortably settled and bound to their specific atoms. They have a home, but they cannot move around the building.

• The Conduction Band (The Party Floor): This is a higher floor with open space. If an electron reaches this floor, it is free to roam all over the material. Moving electrons here create an electric current.

• The Band Gap (The Ceiling / Stairs): This is the empty space between the floors where no electrons are allowed to stay. To get from the home floor to the party floor, an electron must get enough energy to jump the gap

Semiconductors

• Can behave as insulators at neutral state (off)

• When “turned on” become conductors

  • When a voltage is high enough, it “turns on”

• This is because they have a small band gap

• Useful in switching appliances