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AP Physics 2 (2025)

10.3 Electric Fields

2 min readLast Updated on August 14, 2024

Electric fields are fundamental to understanding electromagnetism. They describe the force exerted on charged particles in space, originating from other charged objects. This concept is crucial for explaining various electrical phenomena and forms the basis for many practical applications.

Electric fields can be visualized using vector field maps, showing their direction and strength. In conductors, excess charge distributes on the surface, while in insulators, it spreads throughout. Understanding these principles helps explain how electric charges interact and move in different materials.

Electric Fields

Describe the electric field produced by a charged object or configuration of point charges

Electric fields originate from charged objects ⚡ The electric field at a point equals the electric force exerted on a test charge at that point divided by the charge of the test charge

  • Test charge: point charge small enough that its presence does not significantly affect an electric field in its vicinity
  • Electric field points away from isolated positive charges and toward isolated negative charges
  • The electric force exerted on a positive test charge by an electric field is in the same direction as the electric field Electric field = vector quantity represented in space using vector field maps 🗺️

Describe the electric field generated by charged conductors or insulators

In electrostatic equilibrium, the excess charge of a solid conductor distributes on the surface of the conductor, and the electric field within the conductor = zero

  • At the surface of a charged conductor, the electric field is perpendicular to the surface
  • The electric field outside an isolated sphere with spherically symmetric charge distribution is the same as the electric field due to a point charge with the same net charge as the sphere located at the center of the sphere 🌎 In electrostatic equilibrium, the excess charge of an insulator distributes throughout the interior of the insulator as well as at the surface, and the electric field within the insulator may have a nonzero value

🚫 Boundary Statements: On the exam, students will only calculate electric fields resulting from four or fewer charged objects or systems. Students may analyze electric fields resulting from more charges in situations of high symmetry. Students will only perform qualitative analysis of electric fields within insulators.

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© 2025 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.

© 2025 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.