Resistivity

Voltage source

Device that creates a potential difference

Batteries, generators, and wall outlets

Three examples of voltage sources

Electrical field

What is created when a voltage source is conned to a conductor and that voltage source applies a potential difference on it.

By exerting force on the free charges

How does the electrical field causes current?

The magnitude of the applied voltage and the characteristics of the material that the current is flowing through

Two integral things on which the amount of current depends.

Resistivity

The measure of how much a material can resist the flow of charges

Also called the opposite of the Electrical conductivity

Meaning of crudely analogous

Think of it in that way but don’t take that literally

Electrical field and the properties of the material

Two things on which the resulting current density in the material depends on

J = σE

Formula used to model current density in some materials (including the metals at a given temperature) where the current density is approximately proportional to the electrical field

σ

The symbol that represents the electrical conductivity

Analogous

Means comparable in certain aspect

Thermal conductivity

Electrical conductivity is analogous to what?

Electrical conductivity

Measurement of a material’s ability to conduct or transmit electricity

Conductors

Materials with higher electrical conductivity

Known to have smallest resistivities

Also known to have large free charge densities

σ = J/E

Formula to calculate electrical conductivity

σ = A/V•m

Derived unit for a he electrical conductivity

Ω

Symbol that represents the unit called ohm

1Ω = 1V/A

One ohm = ?

(Ω•m)^-1

Units of the electrical conductivity

Intrinsic property of a material

A property of a material that does not depends on the amount or shape of the material, such property is inherent to the material itself.

Conductivity and electrical resistivity

Two examples of the intrinsic property of the material

ρ

Symbol that represents the electrical resistivity.

ρ = 1/σ

Formula that proves that the Electrical resistivity is the opposite of the Electrical conductivity

(Ω•m)

SI units of resistivity

ρ = E/J

Formula that defines resistivity in terms of the electrical field and the current density

The resistivity is greater

The larger Electrical field is required to produce a certain current density if…

The resistivity is lower

A certain amount of electrical field produces a larger current density if…

Good conductors

Has a high conductivity and low resistivity

Good insulators

Has a low conductivity and high resistivity

Insulators

These materials have the largest resistivity

Most charges in these materials are bound to atoms and are not free to move.

Semiconductors

The type of material that has an intermediate resistivity

These types of material are intermediate;

Have far fewer free charges than conductors but also have properties that make number of free charges depend strongly on the type and amount of impurities in them.

Copper wires

Are routinely used for the extension cords and house wiring

Copper

The element that has the highest electrical conductivity rating therefore has the lowest electrical resistivity rating of all the non precious metals.

In this element the resistivity increases with the increasing temperature.

Tensile strength

A measure of the force required to pull an object to the point where it breaks.

A maximum amount of stress an object can take before the object breaks.

2×10^8 N/m²

The tensile strength of a copper

Ductility

A measure of material’s ability to be drawn into wires and a measure of the flexibility of the material.

Low resistivity, high tensile strength, and high ductility

Three important characteristics for a conductor that makes it a suitable candidate for making wires

Yes, it is true

Is it true that the resistivity of some materials has a strong temperature dependence.

In fact in most of the conducting metals, the resistivity increases with the increasing temperature

vibration, lattice structure, impede

The increasing temperature causes increased __________ of the atoms in the _________________ of the metals, which ______ the motion of the electrons.

Carbon

In this element it’s resistivity decreases with the increasing temperature.

ρ = ρ0[1 + α(T - T0)]

The linear equation that gets used to model the resistivity’s dependance on the temperature being approximately linear in many materials.

T0 = 20.00 °C

Value of T0

α

Symbol that represents the temperature coefficient of a material

ρ0

Symbol that represents the resistivity of a material usually taken at the 20.00°C

Because their resistivity decreases with the increasing temperature

Why does the temperature coefficient value for the semiconductors is negative?

higher temperature, thermal agitation, free charges

Semiconductors become better conductors at a __________________ because the increased _________________ increases the number of ____________ available to carry current.

The type and amount of impurities present in the semiconductor

One more thing that is related with the semiconductor’s property of the decreasing temperature coefficient with the increasing temperature.

Magnetic Resonance Imaging

Full form of MRI

Large Hadron Collider

Full form of LHC

5.95×10^7 (Ω•m)^-1

Conductivity of a copper