A2L Item 127

Goal: Link flux to field lines.

Source: 283-415 nonzero flux?

The circles in the picture below are Gaussian surfaces. All other lines
are electric field lines. For which cases is the flux non-zero?

  1. a
  2. a, b, and f
  3. a, b, e, and f
  4. a, b, d, e, and h
  5. a and b
  6. All but g
  7. All of them
  8. None of the above
  9. Cannot be determined



(2) As “follow-up” it is good to ask questions about comparisons
between two or more of the situations. For example, which is flux is
larger, a or f? Such questions help determine what students are focused
upon; are they keying on number of lines, do they understand that the
flux can be negative.