# Pressure difference

Pressure at a point= hdg where h is height and d is density.Now look at the figure given below.

Here, the pressure is more at point A than the pressure at point B as height of A is more than that of B. So, fluid should flow from A to B as we know that fluid flow from high pressure to low pressure. But in practical life, that does not happen. Why is it so?

226
Abhas Agarwal ·

are the fluid is in a closed container !!!!!! from where does the question of flowing arrives !1 but in case u want to refer to something simmilar to this refer to the topic
SIPHON
VENTURIMETER FROM ANY GOOD BOOK

337
Sayan Sinha ·

No, the fluid is not in a closed container. Fluid always flows from high pressure to low pressure.

• Akash Anand Is pressure difference is the enough condition to flow a liquid?? Or we need something else as well? Think about it.
• Ayush Lodha the pressure difference is enough for the liquid to flow
337
Sayan Sinha ·

Dear Sir,

Liquid also flows from high concentration to low concentration. Since the liquid column above A is more than that of B, a higher density of the liquid is expected at A (since pressure above A is more). So again, the liquid should flow to B.
But, gravity pulls B towards A. This might counterbalance the former statement. But I do not know if it is true.

If required, I can also prove that liquid flows from high pressure to low pressure with practical example.

• Akash Anand Here is the thing, only maintaining potential difference is not enough, we always need a path to flow, if there is no path then fluid wont flow. The condition that you have given, in static condition fluid wont flow at all, in beginning it was not static, so it will follow in a complex path. But once static condition reached then there wont be any flow.
• Akash Anand And the movement you are talking will increase the potential energy of the liquid. Without any external work we cant gain any energy.
337
Sayan Sinha ·

Yes sir,

I understand what you say. Thank you very much for clearing my doubt. This means that fluid will flow from high pressure to low pressure only if it can lose its potential energy.

The proof of the fact that liquid flows from high pressure to low pressure which I was talking about sometime back was from a practical example in which the liquid at high pressure was losing its potential energy. I am ready to give the proof if anyone asks for it.

Thanx once again.