## ~e; fwd: on current and voltage

From human being <human@electronetwork.org>
Date Mon, 17 Nov 2003 14:50:53 -0600

```forwarded with permission...

From   "Skip Leeds" <skip (at) highpineranch.com>
Date   Mon Nov 17, 2003  9:28:45  AM US/Central
To  "'E-Q&A'" <Electronics-qa (at) vk2tips.com>
Subject  RE: [E-Q&A] a basic question (...)

They are two separate electrical properties. Think of the units
involved.

Current is measured in amperes, which is coulombs (charge) per second
(time).  Electrical current is like the current of water in a
river...i.e. how many water particles are going by per unit time. It
doesn't tell you what the water is doing or how energetic it is, it just
tells you how much is moving past a given point for a given amount of
time.

Voltage is measured in volts, which are joules (energy) per coulomb
(charge). In other words, how much energy each unit of charge is
carrying.

Usually, though, voltage is thought of as a difference in potential
between two points. To use the river analogy again -- it's like the
pressure or force at the head of the river, which gives the river its
drive. The reason the river moves is because there's a difference in
pressure at the head of the river vs. the mouth of the river. If the
pressure were the same at both points, the river wouldn't flow, would
it?  It would be at equilibrium.

It's like that with electricity, too...current flows when there is a
voltage difference (or so called "potential") between two points. How
much will it flow?  That depends on the voltage difference between the
two points, and how much resistance to flow exists between the two
points. This, then, is a form of Ohm's Law :

I = V/R
(current is greatest when voltage difference is high, and resistance is
low)

(by the way, some would write this as delta-V, to signify the
*difference* in voltage)

Skip

(...)
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