From: http://webphysics.davidson.edu/Applets/Applets.html

Gauss's law Problem 9.2.1

Description

The bar graph displays the electric flux passing through the cylindrical flux detector.  Drag the surface and observe flux readings. Note:  The Gaussian surface cannot enclose a portion of a line charge but may enclose two line charges.

Question

Which pair(s) of line charges is(are) identical in size but opposite in magnitude? Start Detector

Answer

 A and B and D and E.

Reference

See Giancoli-PA: Appendix D, Giancoli-SE: 22-2.

Credits

Physlet problem authored by Mario Belloni.

© 2000 by Prentice-Hall, Inc. A Pearson Company