The topology of these constructs is given by their helicity, which is the sum of their writhe and twist. For 10 points each:
[10e] Name these vector fields whose lines can be visualized using iron filings and are drawn from the north to south pole.
ANSWER: magnetic fields [accept magnetic field lines; or B-field]
[10m] For a particle in a non-uniform magnetic field, they experience a component of this quantity proportional to the gradient of B. For electrons in a uniform electric field, this quantity equals mobility times electric field.
ANSWER: drift velocity [prompt on drift; prompt on velocity; prompt on u]
[10h] Moving particles in a magnetic field also experience a drift velocity term named for and proportional to this quantity. In MHD, magnetic fields with a non-zero value of this quantity experience magnetic tension equal to this quantity times B-squared over permeability of free space.
ANSWER: curvature [accept curvature drift; prompt on kappa; reject “radius of curvature”]
<WashU A, Physics>