Electric Potential Energy

• In addition to discussing the energy of a "test" charge in a Coulomb field, we can speak of the

electric potential energy of the field itself!

• Reasons?

  • work had to be done to assemble the charges (from infinity) into their final positions.
  • This work is the potential energy of the field.
  • The potential energy of a system of N charges is defined to be the algebraic sum of the potential energy for every pair of charges.

• This theme continues in the course with E in capacitors and B in inductors.

• Let’s start with an example calculation.

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