# Electric charge

A property of matter that comes in two kinds, positive and negative. Like charges repel and unlike charges attract. Charge is conserved and comes in units of e = 1.6e-19 C.

Physics (university) · Part 07: Electric fields and potential · Card 1 of 10 · Last updated 2026-10-19

## Analogy

Static cling is charge moved from one cloth to another.

## Example

**Counting electrons**

e = 1.6e-19 C
N = 1 C / 1.6e-19 C
N = 6.25e18 electrons

## In practice

A charge of 1 coulomb is about 6.24e18 extra electrons.

## Practice

### Flashcards

- **What is the charge of an electron?** About -1.6e-19 C.

## Questions people ask

### How do objects become charged?

Objects become charged when electrons move from one to another, since protons stay in the nucleus. Rubbing a balloon on hair moves electrons to the balloon, leaving hair positive and the balloon negative. Charging by contact or induction works the same way, by moving electrons.

### What does conservation of charge mean?

The total charge in an isolated system never changes. Charge can move around or pair up and cancel, but it is never made from nothing. In a reaction where an electron and positron are created together, the new charges are +e and -e, adding to zero.

## Related concepts

- [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)
- [Field lines](https://studyvisually.com/learn/science/physics-university/physics-university-part-7/physics-university-part-7-concept-4)
- [Gauss's law](https://studyvisually.com/learn/science/physics-university/physics-university-part-7/physics-university-part-7-concept-5)

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