Recent content by lightgrav

  1. L

    I Understanding dissipation of energy in a resistor through the Drude model

    This is essentially the Drude model. In your interpretation, line 1: the electrons don't need to collide with each other if they collide with the lattice. The lattice is not protons (except in Jupiter's core), but rather copper or other metal ion cores. In the "standard intro" Drude model [say...
  2. L

    Errors in Experiment with Low and High Conductivity Materials

    The "V-channel" that collected the melted water - what was it made of? how thick was it? It was touching the ice mold (casing?) wasn't it? was that mold plastic? What was the steam box made from? Was its top surface flat, or did it have a huge hole underneath the material sample?
  3. L

    Magnetic Field of a Line between two wires

    well, the wires just sit there, not going anywhere ... it it their currents that go left and right.
  4. L

    Magnetic Field of a Line between two wires

    both currents make B there into the page ... can these contributions cancel?
  5. L

    Magnetic Field of a Line between two wires

    The place they're asking about is below the top current, and above the bottom current. Yes, the top current makes B inward (x) there ... what does the bottom current do there? btw, it is "same Indicated current" I, but in opposite directions.
  6. L

    Sound Intensity (Level) - Hearing Aid

    They probably meant to say that it amplifies ALL frequencies by 30 dB. "adding" a Bell means multiply the Intensity by 10. +30 dB is +1+1+1 = 3 Bels, so you multiply the Intensity by 10, 3 times.
  7. L

    Finding Vmax of a Block in SHM: Mass, Spring Constant, and Distance

    in oscillations, capital A is the oscillation Amplitude (not the mass) You need to keep track of your UNITS !
  8. L

    Finding Vmax of a Block in SHM: Mass, Spring Constant, and Distance

    ok, that is Time Period and/or angular frequency ... do you want to use Hooke's Law (PE into KE), or do you want to use oscillation formulas?
  9. L

    Wavelengths, Flux Density, Irradiance from a temperature measurement

    If your thermopile is not touching the Al tube surface, it is _deducing_ the Al's temperature from the radiation it receives ... by converting the radiated power that it absorbs into electric voltage (at some efficiency). The (electrical) Power to Heat the tube will eventually raise the tube's...
  10. L

    Electricity (Potential difference between points in circuit)

    There will be counter-clockwise current around the right-hand "loop", and clockwise current around the left-hand "loop". Use these in Kirchoff.
  11. L

    Bifilar pendulum experiment

    if the 2 pendulum strings are attached at the same point, it has become a simple ball-on-string pendulum. (the bifilar's ball motion is the same as for a single string, if the string is shorter.) A torsional pendulum's Restoring Force is caused by a thick support's rotational elasticity, rather...
  12. L

    What is the solution to the cow tipping problem?

    The cow-tipper is pushing with strength Fe , applied to the cow at the top corner, pushing in the optimal direction (perp. to the diagonal). in line 3, the "lever-arm" for the gravity Force (that is, distance from pivot perp. to the weight vector) is x/2
  13. L

    Stiffness constant of a spring

    the pendulum mass has vertical acceleration component (v^2/r) as it swings. The spring must pull the mass upward to provide that acceleration, so the mass pulls the spring downward. If the timing of the pendulum pulls is appropriate, the spring's oscillations will increase in Amplitude...
  14. L

    It is a simple Delta G naught reaction problem

    ok, a Faraday is a mole of electrons, with charge 6E23e/mol*1.6E-19C/e = 96 kC/mol ... Energy = charge * voltage = 2e/molecule * 96 kC/mol *0.24V = 46 kJ/mole. the R is 8.3 J/mole*Kelvin, or =0.0083 kJ/mol*K ... so the moles cancel in the exponent, as they should. I get 9.5E-9 at 300 Kelvin...
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