• Can you kill yourself with a 9 volt battery?

Resistivity

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J =E

ρ

ρ =E

J

ρ =V m

A m2 =V ⋅mA

=V

A⋅m =Ω⋅m

•Current Density of a conductors depends on Electric Field and the properties of the material

•Those properties are symbolized with the Greek letter rho and referred to as resistivity

•The unit for resistivity is Ohm-meters

•Resistivity changes with temperature

Zero-Resistivity Superconductors

Superconductors are used to make medical scanners, magnetometers, and rail guns

Resistivity & Resistance

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R =ρL

A•Unit for Resistance is Ohms (Ω)

•Resistance is higher for wires of longer length

•Resistance decreases with larger cross-sectional areas

Conductance

• The reciprocal of Resistance

• Lord Kelvin called the unit the mho

• Officially the Siemens

• 1 mho = 1 Siemens

Ohm’s Law

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E = ρJ

V

L=I

Aρ

V = IρL

AV = IR

Units

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V = IR

Volts = Amps⋅Ohms

Ohms =Volts

Amps

I-V Graph for Ohmic Material

Diode: Ohmic or Not Ohmic?

Guess the Resistors!