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PRACTICE / Electric field

Do the electric fields cancel at the midpoint?

A +2 nC charge is fixed 0.30 m left of a midpoint. A −2 nC charge is fixed 0.30 m right of it. Use k = 9 × 10⁹ N m²/C².

+2 nC−2 nCMidpoint0.30 m0.30 m
Work out each field direction at the marked midpoint.

What is the electric field at the midpoint?

Organize the givens & assumptions
  • Left charge: +2 nC
  • Right charge: −2 nC
  • Distance from each charge: 0.30 m

Point charges in vacuum, with no other electric fields. Take right as positive.

  1. A00
  2. B200 N C−1 right200\ \mathrm{N\,C^{-1}}\ \text{right}
  3. C400 N C−1 left400\ \mathrm{N\,C^{-1}}\ \text{left}
  4. D400 N C−1 right400\ \mathrm{N\,C^{-1}}\ \text{right}

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