You need to create a certain amount of pressure difference right, suppose you take a pipe then to, then to be able to create a certain amount of flow through the pipe, you need to create a certain amount of pressure difference across the two ends of the pipe.
आपको एक निश्चित मात्रा बनाने की आवश्यकता है, ठीक हैं, मान लीजिए कि आप एक पाइप करते हैं,