ElectromagnetismLesson 2 of 3 in the course Electric Charges and Fields

Electric Field Lines: Direction, Density, and Diagram Rules

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Electric field lines provide a visual way to represent the electric field created by source charges. They turn information about the field’s direction and strength into a diagram that is often easier to interpret than many separate arrows.

A source charge changes the space around it. A test charge placed in that region experiences an electric force. The electric field at a point is defined by the force that a hypothetical positive test charge would experience there, per unit charge.

All flashcards

Electric-field direction
The direction of the force on a hypothetical positive test charge at that point.
Field-line tangent
The electric-field vector points along a field line’s local direction.
Field-line density
The number of lines per area; greater density represents a stronger field.
Field-line count and charge
Within one diagram, the number of lines associated with a charge is proportional to its magnitude.
Why field lines cannot cross
A crossing would assign two different electric-field directions to the same point.

Quiz questions

  1. Where do electric field lines begin and end?Answer: They begin on positive charges or at infinity and end on negative charges or at infinity.
  2. Why can electric field lines not cross?Answer: A crossing would give the electric field two directions at one point.
  3. In a single electric-field diagram, what does twice as many lines associated with one charge indicate, compared with another?Answer: The first charge has twice the magnitude of the second charge.
  4. A charge arrangement has more positive charge than negative charge overall. What happens to the unmatched field lines from positive charges?Answer: They extend outward to infinity.
  5. What do the drawn lines in an electric-field diagram represent?Answer: A visualization of a continuous field, not separate physical strands.

Based on University Physics Volume 2 by Samuel J. Ling, William Moebs, Jeff Sanny (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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