S13Phys2BaLec26A

# You basically want to measure what the potential was

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You basically want to measure what the potential was before the element and what the potential is after the element.

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Voltmeter “Feel & compare” before/after + V
Resistivity If I were constructing a wire, for a given battery how could I increase the current flow in the wire? Use a good conductor. Increase its cross-sectional area. Shorten its length. ρ is resistivity (depends on the type of material of the conductor). L is the length of the conductor and A is the cross-sectional area of the conductor. The resistance, R, of a conductor is given by:

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Resistivity Resistivity is measured in units of: [ Ω m] Insulators have very high resistivity: We can also talk about how easily it is for charge to flow through a material. We define conductivity, σ , this way: Metals typically have very low resistivity: Conductivity is measured in units of: 1/[ Ω m]
Ohm’s Law Ohm’s Law quantifies the ability of a given material to resist the flow of charge for a given electric potential difference. where R is the resistance and is measured in Ω (Ohm’s). [ Ω ] = [Volt]/[Ampere]

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V , R “Dwelling Fire—Gloucester City” (Source: Ron Trout/PFN Staff) M ore I current
V , R “Kink?” (Source: Stephen “srdreed”) L ess I current

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Ohm’s Law A good conductor will have a low resistance, this means that current will easily flow through it. A good insulator will have a high resistance, this means that current will have a very hard time flowing through it. With Ohm’s Law, as you increase electric potential ( Δ V), then current will increase linearly. The resistance in a circuit arises due to collisions between the electrons moving against the electric field and the electrons that are fixed in the atoms.
Resistivity

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• Spring '08
• schuller
• Physics, Potential difference, Electric charge, Integrity of Scholarship

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