Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

If the quarks in a neutron are (up,down,down), why isn't it negatively charged? Excuse the silly question, just wondering.

share|cite|improve this question
Because the quarks have fractional charges that cancel. – Brandon Enright Feb 14 '14 at 6:24
It's worth mentioning that while its net charge is zero, the neutron has a non-null charge distribution, something like this. – giordano Feb 15 '14 at 19:21
up vote 20 down vote accepted

The up quark has a charge of $+2/3$, the down has a charge of $-1/3$. If you have a bound state of charged particles, the total charge is just the charge of the elementary constituents. The neutron consists of one up quark and two down quarks, so the total charge $Q$ is:

$$Q = 2/3 + 2 \times (-1/3) = 0$$

share|cite|improve this answer

The names up and down don't refer to electric charge $Q$ but are rather references to isospin charge $I_3$.

share|cite|improve this answer

A neutron consists of three quarks $u d d$(up down down quarks). The up quark(u) carries charge $2e/3$ and the down quark(d) carries a charge $ -e/3 $. Thus $2e/3-e/3-e/3=0$

share|cite|improve this answer

Because $2/3-1/3-1/3=0 $.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.