nagle_phys2020_fa07_lecture15

nagle_phys2020_fa07_lecture15 - Clicker Question An ideal...

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1 1 Clicker Question An ideal battery produces a fixed? A)Current Output B)Electric Potential Energy Output C)Power Output D)Electric Potential Difference E)None of the Above 2 Most materials are Ohmic . In Ohmic materials, the current (i) is proportional to the electric field or the electrical potential difference (V). High V Low V E d d E V V | | v = Δ = V i (Ohmic mat.) constant = i V 3 Resistance R of a piece of wire (or other material) constant = i V R Definition of R “Ohm’s Law” iR V = This is not really a physical law. It is true for perfectly Ohmic materials. Resistance has units of Ohms = Ω = Volts/Amp 4 High resistance == lots of scattering (internal friction) Inside a metal, electrons have net movement when non-zero E. a m E q F v v v = = Scattering Æ electron speed up or slow down Electrons reach “terminal velocity” = v d = drift velocity 5 Estimate the drift velocity of electrons in a #18 gauge (1 mm) copper (Cu) wire with 1 Ampere of current?
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nagle_phys2020_fa07_lecture15 - Clicker Question An ideal...

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