# Field lines

Lines that show the direction of the field. They start on positive charge, end on negative charge, and are closer where the field is stronger.

Physics (university) · Part 07: Electric fields and potential · Card 4 of 10 · Last updated 2026-10-19

## Analogy

Wind arrows on a weather chart.

## Example

**Reading lines**

Dense lines: strong field.
Parallel lines: uniform field.
Start +, end -.

## In practice

Field lines never cross because the field has one direction at each point.

## Practice

### Flashcards

- **Where do field lines start and end?** Start on positive charge and end on negative charge.

## Questions people ask

### Why can't field lines cross?

If two lines crossed, the field at the crossing point would have two directions at once. A charge placed there would not know which way to be pushed. The field has one definite direction at every point, so the lines of force can only touch at a zero-field point or end on charges.

### What do equipotential lines show?

Equipotential lines connect points at the same voltage. They always cross field lines at right angles, and no work is done moving a charge along one. Like contour lines on a map, close lines mean a steep change and a strong field.

## Related concepts

- [Electric charge](https://studyvisually.com/learn/science/physics-university/physics-university-part-7/physics-university-part-7-concept-1)
- [Coulomb's law](https://studyvisually.com/learn/science/physics-university/physics-university-part-7/physics-university-part-7-concept-2)
- [Electric field](https://studyvisually.com/learn/science/physics-university/physics-university-part-7/physics-university-part-7-concept-3)
- [Gauss's law](https://studyvisually.com/learn/science/physics-university/physics-university-part-7/physics-university-part-7-concept-5)

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