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QPages 140-141: Q7: HC Verma: Concepts of Physics - Volume 2 Gauss's Law Pages 140-141: Q7 Solution: A closed surface S is constructed around a conducting wire…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often mistake the presence of a steady current through a Gaussian surface for a change in net charge, assuming the electric flux must vary. Remember Gauss's law links flux only to the total charge inside; if as many electrons enter as leave, the enclosed charge stays zero and the flux remains unchanged.

A closed surface S is constructed around a conducting wire connected to a battery and a switch in the following figure. As the switch is closed, the free electrons in the wire start moving along the wire. In any time interval, the number of electrons entering the closed surface S is equal to the number of electrons leaving it. On closing the switch, the flux of the electric field through the closed surface

Multiple Choice Options

  • A is increased
  • B is decreased
  • C remains unchanged
  • D remains zero

Step-by-Step Verified Solution

**Answer:** (c) remains unchanged. **Step-by-Step Explanation:** The net charge enclosed by the surface remains zero, so the flux remains unchanged.

All Questions in this Chapter

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