Question
Two answers required. The dot product of these two quantities is added to the divergence of the Poynting vector in Poynting’s theorem to represent the rate of work on charges. For 10 points each:
[10h] Name these two quantities whose ratio equals resistivity according to a “continuum” form of Ohm’s law that is derived by dividing both sides by length.
ANSWER: electric field AND current density [accept in either order; accept E-field instead of “electric field”; prompt on E instead of “electric field”; prompt on j instead of “current density”]
[10m] Poynting’s theorem gives an equation for this operation on negative energy density. Applying this operation to charge yields current.
ANSWER: partial time derivative [or partial derivative with respect to time or differentiation with respect to time; prompt on partial derivative by asking “with respect to what quantity?”; prompt on answers describing dividing by time by asking, “what is the analog of that operation in calculus?”]
[10e] The Poynting vector equals the cross product of the electric field and the field “auxiliary” to this field, which is denoted with a bold “B.”
ANSWER: magnetic field
<David Bass, Science - Physics> ~22502~ <Editor: David Bass>
Data
Summary
| Tournament | Edition | Exact Match? | Heard | PPB | Easy % | Medium % | Hard % |
|---|---|---|---|---|---|---|---|
| 2024 PACE NSC | 06/08/2024 | Y | 36 | 16.11 | 89% | 69% | 3% |