MadSci Network: Physics
Query:

Re: Why do you see lightning and sparks but not other electricity?

Date: Mon Mar 12 14:01:27 2001
Posted By: Shel Randall, System Consultant
Area of science: Physics
ID: 984337779.Ph
Message:

Before I answer your question, I want to make sure you understand some things about electricity.

I wrote a LOT of stuff for you, so I hope it helps you. I tried to answer your question at the end.

About Charges and Ions...

There are particles and groups of particles all around us that have a "charge", which can be positive or negative.

Negative and positive charges attract each other. When they get together, they "cancel out"... the total charge is zero.

For example, an atom that has more protons than electrons will have more positive charges than negative charges. When you add them all up, the total is positive. This type of atom is called a "positive ion".

An atom with more electrons than protons is a "negative ion".

And when they balance out, it's just a neutral atom, with no charge.

Big Positives, Small Negatives...

Typically, the positive particles (protons floating around, or atoms with a positive charge ("positive ions"), etc.) are bigger and heavier (and slower) than the negative particles (electrons floating around, negative ions, etc.).

Protons are bigger and heavier than electrons.

So, it's easier for electrons to move around. Protons move too, but since electrons do most of the moving, we call it "electricity", instead of "protricity". Makes sense, right? ("protricity" is not a word. I made it up.)

Be The Electron...

Pretend you're an electron. You are attracted to a positive charge. Are there any around? They are all over the place! Pick one. You probably would prefer the closest one. Is it easy to get to? Maybe, maybe not. There might be something in the way.

Find The Easiest Path...

If there are a lot of things in the way, you might want to try looking for a positive charge that's not so close, but easier to get to.

You will want the find the EASIEST way (the easiest "path") to get to the strongest positive charge nearby. The EASIEST path may not be the shortest path.

That's why lightning looks crooked instead of straight.

Speed is Like Voltage...

If it's a STRONG positive charge, then you will want to move faster toward it. In fact, the difference between your negative charge and that positive charge, is called "voltage", "potential difference", or also "electromotive force".

The bigger the charge difference, the bigger the voltage. Voltage makes an electric field.

The bigger the voltage, the stronger the electric field between you and the positive charge, and the faster you will move.

When the voltage is big (when the voltage is "high"), particles (like electrons) can move over larger distances faster.

In fact, you can almost tell what the voltage is by measuring the length of the spark.

Short spark = low voltage.
Long spark = high voltage.

(I'll let you figure that out by yourself.)

Friction...

Think of voltage like a hill.

The bigger the voltage, the steeper the hill, and you will roll down it faster.

If there is stuff in your way now, you may be moving fast enough to knock it aside.

That would be like "friction".

You might even be moving so fast, you will knock some electrons off of some neutral atoms. That would turn them into "ions" and you would be "ionizing" the air.

When you have a lot of these broken atoms floating around without moving too much, we call that "static electricity".

A Lot of Charges is Current...

If you had a LOT of negatively charged friends, and you all moved together, that would increase the "current" or "amperage".

The more charged particles that move, the bigger the current. And when you all move together really fast, you're going to be knocking a LOT of things out of your way. That's a LOT of friction, and causes a lot of broken atoms. Ouch.

Making Lightning...

Now, you are still an electron. You and billions of your electron friends are sitting around on the ground.

Above you is a big cloud. You start to get a tingly feeling. You feel an electric field.

There is a big difference between your charge and something nearby. It's the cloud! It's got a lot of positive charge! It's a BIG difference... a LARGE voltage.

You feel like you're getting ready to move REALLY fast.

All your friends feel it too. They are ALL getting ready to move REALLY fast. And then, you do. All at once.

Somebody found an easy path to the cloud and everybody went the SAME WAY.

It was a LARGE crowd moving VERY FAST. Lots of current, lots of voltage. Lots of energy. And all you guys pushed a LOT of atoms in the air OUT OF THE WAY VERY FAST. Lots of friction. It's a lightning bolt.

All that energy makes a lot of heat, noise and light. You hear the noise as thunder. You see the light as lightning. And if you're unlucky enough to be in the way, you FEEL the heat as getting cooked. Super-ouch!

Making Sparks...

Sparks are just tiny, tiny lightning bolts. Just a FEW million particles (a small "current"), not moving very fast (a small "voltage"), over a short distance.

But when they all move together, you still get the friction, and the heat, light and sound. You see the light and hear the little "Bzzzt" or "Pop" of the spark, but you hardly feel the heat.

Little things will feel the heat though. To a little bug, a spark is like a lightning bolt. To a little computer part, it's like a lightning bolt too.

That's why you need to make sure there are no sparks around tiny computer parts. The spark won't hurt you, but it will cook those little parts, and ruin the computer.

Invisible Electricity...

If the electrons are moving through the air, you will see the light and hear the sound. But if they move inside something, like a wire, there is nothing for you to see.

When water flows along a river, you see it, but when it's in a pipe you don't, right? Wires are like electricity pipes.

Most common wire is made of copper or aluminum, which are very "conductive" metals. This means they let the electrons move along without getting in the way too much. So there isn't as much friction.

If you allow a LOT of electricity (a LOT of "current") to go through a tiny wire, there will be friction, and the wire will heat up, and maybe melt. (This is how fuses and light bulbs work.)

Light Bulbs...

When a light bulb lights up, you're not exactly seeing the electricity moving directly; you're seeing the tiny metal wire heat up and glow from the heat.

Fuses...

A fuse is a tiny wire that is SUPPOSED to melt if TOO MUCH current goes through it. When the fuse melts, it break the electrical circuit, and the electricity stops. This protects other things on the wire (like appliances, computers, etc.) so THEY don't melt instead. Computers are expensive; fuses are cheap... I would rather replace the fuse than the computer.

I hope this answered your question. Thanks for asking!


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