A2L Item 132

Goal: Link energy conservation and electromagnetism

Source: 283-421 Change of total energy

uniform volume distribution of charge has radius R and total charge Q.
A point charge -q is released from rest at point b, which is a distance
3R from the center of the distribution. When the point charge reaches a,
which of the following is true regarding the total energy, E?

  1. Ea = -Eb
  2. Ea = -2Eb/3
  3. Ea = -3Eb/2
  4. Ea = -9Eb/4
  5. Ea = Eb
  6. Ea = 2Eb/3
  7. Ea = 3Eb/2
  8. Ea = 9Eb/4
  9. None of the above
  10. Cannot be determined



(5) Students often forget to include the kinetic energy,
especially after a lot of discussion of potential energy. Many will
simply misinterpret the energy to mean potential energy. Teasing apart
these issues is important.