# Why do tankers be charged

1. Apr 14, 2010

### pixel01

As you know some trucks (tankers) always have a chain or wire underneath to discharge electricity. My question is where has the charge come from?

Last edited: Apr 14, 2010
2. Apr 14, 2010

### PaulS1950

Static electricity is generated by the tires and the air moving over the surface of the trucks body and tank.

3. Apr 14, 2010

### pixel01

Thanks,
So what dominates the charge: the tires or the moving air?
I myself sometimes create sparks when touching the door knob. Quite strong. No air moving, so maybe it's only the tires?

4. Apr 14, 2010

### PaulS1950

The amount of charge of the air depends on the velocity, temperature and humidity and the amount of charge developed by the tires depends on the materials involved. (the composition of the tires and road surface.

5. Apr 14, 2010

### pixel01

But we don't know what is the dominant. Possibly that the tires can make up 99% of the charge, and we can neglect the air. Say, the airplane, it fly very fast and I do not know if if has problem with charge caused by the moving air.

6. Apr 14, 2010

### turbo

Google on airplane static discharge. It's not the tires that is dominant in accumulating charge in airplanes.

7. Apr 14, 2010

### pixel01

Sure that the tires do not dominate the charge in airplanes. They taxi very slowly and just some km on runway.

8. Apr 14, 2010

### Frame Dragger

I would start with Van de Graaff Generators, and work up to trucks. The principle is the same, and while the tires carry some charge, it's hardly a belt with combs. Imagine a volcanic eruption of a stratovolcano: The small particles cause large charges to build in the plume, hence SERIOUS air-air lightning.

Consider the road vs. dry cool air, striking the (essentually) hollow metal box, that is most of a truck: that is a LOT of charge being exchanged, compared to rotating tires which would tend to discharge on their own more than simply carry the charge to the truck's body.

EDIT: Hmmmm... then again, truck tired are steel belted... I wonder what effect that has. Can the tires act a bit like capacitors? Even then collision with air and dust (pollen, etc) would be a greater factor.

9. Apr 14, 2010

### turbo

No. The primary cause is static charge resulting from the dry air rubbing on the skin of the airplane. Did you google on "airplane static discharge"? It would help settle the needless speculation.

10. Apr 14, 2010

### pixel01

I have not googled, but the 2 cases are quite different. Airplanes fly very fast, the friction caused by moving air is big. But the truck moves much slower and the tires always have friction with the surface of the road. My speculation is about the truck.

11. Apr 14, 2010

### Frame Dragger

*Faceplam*

12. Apr 14, 2010

### pixel01

???

I guess you all have experienced electric shocks (sometimes, not gentle) while walking in a supermarket and unattentively touch the trolley or somethings. That's all for friction of the shoes and the floor, not the air moving.
So in the case of trucks, I am not sure if the tires are the dominant or just moving air.
I thought it's only because of the air.