# I Pressure changes of a fluid flowing through a horizontal pipe

#### Photo1234

If we have a tube of fluid going like it is shown in the picture, and we measure pressure at two points we would get the same value. But the fluid is still going from point A to point B. So is pressure difference not necessary for fluid flow or I made some other wrong assumptions?

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#### jbriggs444

So is pressure difference not necessary for fluid flow
Newton's first law. An object in motion will continue in motion at a constant velocity unless acted on by an outside force.

#### Orodruin

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If friction and viscosity is significant you will need a pressure gradient to drive the flow. If they are not, the pressure in the two points will be the same.

• russ_watters and Chestermiller

#### Photo1234

What if we use electrons instead of fluid and use Ohms law V = R * I for two points like that, and If V = 0, that current should also be 0. Is that violation of Omhs law?
(We neglect resistance of the wire)

#### anorlunda

Mentor
What if we use electrons instead of fluid and use Ohms law V = R * I for two points like that, and If V = 0, that current should also be 0. Is that violation of Omhs law?
(We neglect resistance of the wire)
No it is not a violation and it does not need us to neglect the resistance. Let us say R=1, Then V=R*I means 0=1*0. Same answer if R=1000.

#### Photo1234

If we look at two points with the sam voltage in the circuit, then V=0, and R=0, but current flows.

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#### anorlunda

Mentor
Did you understand the answer in post #3?

#### Photo1234

So I = V/R = 0/0

And what causes current if not voltage? Inertia?

#### russ_watters

Mentor
So I = V/R = 0/0

And what causes current if not voltage? Inertia?
You're trying to find a physical meaning for an assumed - not real - mathematical result of 0/0. There really isn't one. Stick to the physical laws. Stick to the answer you got in post #3 and recognize that simplifications are sometimes useful, but sometimes give nonsensical results.

#### Photo1234

You're trying to find a physical meaning for an assumed - not real - mathematical result of 0/0. There really isn't one. Stick to the physical laws. Stick to the answer you got in post #3 and recognize that simplifications are sometimes useful, but sometimes give nonsensical results.
What abaut this:
And what causes current if not voltage? Inertia?

#### anorlunda

Mentor
Sorry, this question has been answered several times.

@Photo1234 go back and re-read the answers.

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