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WHAT'S THE DIFFERENCE BETWEEN
ELECTRIC CURRENT AND
NET ELECTRIC CHARGE?
1999 William Beaty
Also see: What's the difference between Static
Electricity and Current Electricity?
"Net Charge" and "Electric Current" are two different things that
electric
charges can do. First things first:
What is Electric Charge?
Everyday objects are made of Electric Charge: objects are
made of molecules, molecules are made of atoms, and atoms are made of
positive and negative charges. Electric charge is a kind of material
substance, but it is not atoms. Instead it is the stuff that is inside
of the atoms. If we could place equal quantities of positive charge and
negative charge together, what would be the result? Neutral matter.
What is Static Electricity?
If you've read my other articles, you'll know that the term 'Static
Electricity' is somewhat misleading. It has little to do with anything
being "at rest." And don't even get me started about that word
"Electricity!" Let's ask our question this way instead: when we rub a
balloon on our hair, some strange and invisible stuff appears on the
balloon (and on our hair too.) WHAT IS THAT STUFF?
The "stuff" on the balloon is electric charge. But wait a minute. The
balloon itself is supposedly made of electric charge, since the
atoms of the rubber contain electrons and protons. Why does rubbing the
balloon on my head make the charges act differently? Easy answer: the
balloon (and everything else) is made of CANCELLED-OUT electric charges,
where the amounts of positive charge and negative charge are perfectly
equal. Everyday matter is made of "neutralized charge." But that
"stuff" on the surface of the rubbed balloon is different. It's a tiny
amount of UNCANCELLED, non-neutral electric charge.
By rubbing balloons on our heads, we make the rubber grab some negative
charge out of our hair. Before the negative charge was grabbed, our hair
contained perfectly equal quantities of positive and negative. When the
negative charge departs, our hair then is left with excess positive
charge, while the balloon now has some excess negative charge. When we
pull the balloon away from our hair, we "un-cancel" the opposite charges
of the matter. We separate them.
See: Red and Green
Electricity
The words "static electricity" are often used to mean "uncancelled
electric charge." Therefore, when we claim to be "generating static
electricity", what we're REALLY doing is grabbing the positive and
negative bits of matter, then pulling them away from each other. "Static
electricity" is not charges at rest, it is opposite charges which are
separated, or imbalanced, or "un-cancelled."
Rather than calling it "static", a better word for this is "net charge."
The balloon ends up with more electrons than protons, so it has a NET
NEGATIVE CHARGE. Our hair ends up with fewer electrons than protons, so
it has a NET POSITIVE CHARGE.
What is Electric Current?
Back to the everyday objects again: objects are made of molecules,
molecules are made of atoms, and atoms are made of electric charges.
Therefore when you look at an object, don't imagine that it is made of
little tiny atoms. Instead, imagine that it's made of something even
smaller: little tiny electric charges. Matter is made of vast quantities
of electric charge, but the positive charge exactly cancels the
negative.
Wait a minute. Why should we pretend that matter is charges, when it's
REALLY atoms? Atoms might be made of charges, but atoms are unbreakable,
right? Wrong. Atoms are easily broken up. It is the NUCLEUS of an atom
which is difficult to shatter. It's quite easy to shred atoms by pulling
the negative electrons away from the tiny positive nucleus in the center
of an atom. When we rubbed the balloon on our hair, we were pulling atoms
apart. We should not think of atoms as if they were unbreakable little
solid balls. Atoms are more like liquid droplets made of electrical
charge. When atoms come together to form everyday objects, the charges
which form the outside of the atoms get all mixed together. It's as if
the objects in our world were made of charged particles, half of them
being the negative electrons, and the other half being the positive cores
of atoms.
What would happen if we could make the electric charges flow around inside
of an object? AHA! Then we would have an electric current. Now you know
what an electric current really is. It's that simple: an electric
current appears whenever the negative charges in an object are forced to
flow through the positive charges, or when positive charges are forced to
flow through negative ones. Or when the positives and negatives are
forced to flow in opposite directions at the same time.
How are "Static" and "Current" different?
If you know a little bit about separated (un-cancelled) electric charge,
and if you also know about charge flow, then you should be able to answer
the above question on your own. Here's my answer:
All matter is made of enormous quantities of positive and negative charge
in perfect balance. When opposite charges flow in the same direction, we
have PHYSICAL MOTION. Whenever the opposite quantities of charge are
forced to flow in two different directions, we have an ELECTRIC CURRENT.
Whenever the positive charge is separated from the negative charge, we
have NET ELECTRIC CHARGE.
Is "Static" the opposite of "Current"
Most elementary school books say something like this: THERE ARE TWO KINDS
OF ELECTRICITY, STATIC ELECTRICITY AND CURRENT ELECTRICITY. STATIC
ELECTRICITY IS ELECTRICITY AT REST, WHILE CURRENT ELECTRICITY IS
ELECTRICITY IN MOTION." As you might guess, I have certain words to
describe this. "A bunch of Hooey" is the milder version. There are NOT
two kinds of charges called "static" and"current!" And that stuff about
"electricity at rest" is simply wrong.
When we create a separation-of-opposite-charge, we are "stretching" the
positive and negative charges apart ...and they will snap back together if
given the chance. Opposite charges attract, and they behave as if they
are connected by invisible rubber bands. Does "stretched charge" have
anything to do with "charges at rest?" No. Stretched rubber bands aren't
called "Static Rubber." Imbalances of charge have nothing to do with
motionlessness. And static is not the opposite of current: net-charge is
not the opposite of flowing charge. Whether it flows or whether it remains
still, the so-called "static charge" is charge that is uncancelled, it's
charge that's missing its opposite partner. Charge can flow along during
an electric current, and if the flowing charge is charge of the
un-cancelled type, then "static electricity" is flowing along! "Static"
that MOVES. But this is OK, since "static electricity" is not the
opposite of "electric current," any more than "stretched" is the opposite
of "moving."
To get a "visual" viewpoint on all of the above try:
EXPLAINING ELECTRICITY WITH RED AND GREEN PLASTIC SHEETS
The Electricity Map
'Static' Electricity that Flows
Electricity Misconceptions
Misconception References
All Electricity Articles
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