Pressure and Flow Rate

Voltage (also known as potential) acts as a sort of pressure, causing current to flow. This is like water pressure, causing water to flow. High pressure causes a rapid flow; lower pressure causes slower flow. If there is no pressure at all, there is no flow.

You can see an example of this in the flow of water out of a picnic cooler. Water towers work on the same principle.

In an electrical circuit, the pressure is often provided by a battery or some other voltage source. In response to this pressure, current flows through the circuit. The flow of current through the filament of a light bulb causes it to glow. Lots of current makes it glow brightly. With less current, it is dim.

Sometimes someting gets in the way and partially blocks or slows the flow. With water flow, this may be a narrow section in the pipe or hair in a drain. With electrical flow, something that slows the flow is known as resistance.

These applets were written by Lisa Denise Murphy at the University of Illinois. Early drafts were written in 1999. The current version was last revised in January of 2000. Permission is given for students and teachers to use these applets, provided acknowledgement is made of the source. Anyone interested in using these applets in connection with any published paper or commercial venture should please first consult the author. Thank you.

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This page last revised January 15, 2003.