# Interaction of particles

1. Oct 29, 2013

### Hluf

Hi people,
I have one question, leptons and quarks are electromagnetically charged particles. Is there an electromagnetic interaction between them?
Thank you for the help!

2. Oct 29, 2013

### Staff: Mentor

Of course. That's how electrons and protons stay bound to each other in atoms.

3. Oct 29, 2013

### Hluf

Thank you, electrons and protons stay bound to each other in atoms because they have an integer charge but quarks have a fractional charge how they interact with leptons?

4. Oct 29, 2013

### Bill_K

Charges with opposite sign attract, and charges with the same sign repel. It has nothing to do with whether they are integer charges or not.

5. Oct 29, 2013

### Hluf

According to the strong interaction, we can never see free quark, so how can the electron interact with up-quark or down quark? thank you for the response!

6. Oct 29, 2013

### Staff: Mentor

Why wouldn't it be able to? A free quark just means a quark that isn't bound together with another quark. There's still three quarks making up each proton.

7. Oct 29, 2013

### ZapperZ

Staff Emeritus

First, you asked if there's any electromagnetic interaction between quarks and leptons. Presumably, you have no problem with knowing that there is an electromagnetic interaction between protons and electrons, ya?

So, naturally, I puzzle over why there is a problem with accepting that there is an electromagnetic interaction between quarks and leptons. After all, a proton is made up of 3 quarks. So if proton-electron has EM interaction, why do you have a problem with quark-lepton? having EM interaction?

Secondly, why would "strong interaction" matter on whether there is EM interaction between quark-lepton, which was your original question? It is not an either-or situation. The strong interaction only matters between quark-quark (or any hadrons). It doesn't significantly affect the EM interaction between quark-lepton. So I am puzzled why this matters. Does the fact that my charged Van de Graaf generator is on the earth, in the gravitational field, significantly affects its EM field when compared to having it float in space when there's less gravitational field?

Zz.

8. Oct 29, 2013

### clem

The EM interaction is long range, so it doesn't matter where the quark is.

9. Oct 30, 2013

Thank you.