Practice question · Sort into groups
Sort each statement by whether it describes the charge picture or the field picture of electrostatic energy.
Groups: Charge picture · Field picture
- Indispensable once radiation carries energy away
- Energy is one half the sum of q times V over all charges
- The factor of one half prevents double-counting each pair
- Energy density is one half epsilon-zero E squared
- Energy is obtained by integrating over all space
Hints
- One picture sums over charges, the other integrates over space.
- Both give the same total; only one still works when the charges are long gone.
Show the answer
Charge picture: Energy is one half the sum of q times V over all charges, The factor of one half prevents double-counting each pair
Field picture: Energy density is one half epsilon-zero E squared, Energy is obtained by integrating over all space, Indispensable once radiation carries energy away
Why
Both descriptions give identical totals for a static configuration. The field picture becomes indispensable for radiation, where energy is demonstrably travelling through space rather than sitting on any charge.
Practise Electrostatic Energy and Forces
The app has 4 more questions on this lesson, and keeps your place in the course. Physics II is free to start.
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