3 seemingly dumb questions from a newbie

[Obba]

Hi all,

 

I'm new to this SFN forum and thought i would ask a few 'simple' questions.

 

1) I was told that an Atoms would be the size compared to a Molecule - as in the Earth being made solidly of grapes: IE, Each grape on scale is an Atom.

This seemed a little to small, what are your opinions?

 

2) Whilst water (pure), does not conduct electricity and Petrol does not ignite (Only the fumes). Someone brought this to my attention - Electricity does not flow.

I have read a bit about this and besides (the change of the 'flow' of direction from Neg to Pos in the science books of old- it now seems to be Pos to Neg - welcome to Entropy!), but there are quite a few articles out there mentioning that there is no Flow.

 

3) Is Magnetisuim (sorry about the speeling , the same as Electricity, as in static electricity, North-South / Pos-Neg?

 

Anyones thoughts on those would be most welcome and i promise that i will remember you when i am drinking my winnings

 

Thanks,

 

Alan.

[BobbyJoeCool]

1) I was told that an Atoms would be the size compared to a Molecule - as in the Earth being made solidly of grapes: IE' date=' Each grape on scale is an Atom.

This seemed a little to small, what are your opinions?[/quote']

 

Atoms

Atom sizes

The size of an atom is not easily defined since the electron orbitals just gradually go to zero as the distance from the nucleus increases. For atoms that can form solid crystals' date=' the distance between adjacent nuclei can give an estimate of the atom size. For atoms that do not form solid crystals other techniques are used, including theoretical calculations. As an example, the size of a hydrogen atom is estimated to be approximately 1.2×10-10m. Compare this to the size of the proton which is the only particle in the nucleus of the hydrogen atom which is approximately 0.87×10-15m. Thus the ratio between the sizes of the hydrogen atom to its nucleus is about 100,000. [u']Atoms of different elements do vary in size, but the sizes are roughly the same to within a factor of 2 or so. The reason for this is that elements with a large positive charge on the nucleus attract the electrons to the center of the atom more strongly.[/u]

 

And molecules

Molecules

Under normal conditions molecules have a dimension of a few to a few dozen Å.

 

Angstrom (Å)=10^-10 m (or 0.1 nm)

 

so, molecule =0.2 nm-3.6 nm and an atom = .12 nm-.24 nm. Approx...

 

So a Large molecule is 3.6 nm, and a small atom is .12 nm. ratios! .12:3.6... 1:30. so a large molecule is about 30 times bigger than small atom. Grape and Earth? not really. Maybe if you're talking about an object being made up of molecules... then you have several million or billion molecules making up an object, but there are rarely that many atoms in a molecule.

 

2) Whilst water (pure)' date=' does not conduct electricity and Petrol does not ignite (Only the fumes). Someone brought this to my attention - Electricity does not flow.

I have read a bit about this and besides (the change of the 'flow' of direction from Neg to Pos in the science books of old- it now seems to be Pos to Neg - welcome to Entropy!), but there are quite a few articles out there mentioning that there is no Flow.[/quote']

 

is this what you mean?

 

Electric Current

A flow of electric charge is called an electric current. A direct current (DC) is a unidirectional flow; alternating current (AC) is a flow whose time average is zero, but is not zero at all times. That definition of AC implies that the flowing electric charge repeatedly changes direction. (Polarity and numerical sign (i.e. negative vs. positive) are additional terms for direction in this sense).

 

Otherwise, if you have a curcular current (like in a circit (sp)), it flows from positive to negative to positive to negative to positive to negative...

 

3) Is Magnetisuim (sorry about the speeling , the same as Electricity, as in static electricity, North-South / Pos-Neg?

 

Magnetism

In physics' date=' magnetism is one of the phenomena by which materials exert an attractive or repulsive force on other materials. Some well known materials that exhibit easily detectable magnetic properties are iron, some steels, and the mineral lodestone; however, all materials are influenced to one degree or another by the presence of a magnetic field, although in most cases the influence is too small to detect without special equipment.

Magnetic forces are fundamental forces that arise due to the movement of electrical charge. Maxwell's equations describe the origin and behavior of the fields that govern these forces (see also the Biot-Savart law). Thus, magnetism is seen whenever electrically charged particles are in motion. This can arise either from movement of electrons in an electric current, resulting in "electromagnetism", or from the quantum-mechanical orbital motion (there is no orbital motion of electrons around the nucleus like planets around the sun, but there is an "effective electron velocity") and spin of electrons, resulting in what are known as "permanent magnets".[/quote']

 

Electricity

When the early scientists talked of 'electricity' what they were actually referring to was 'charge'. Present usage of the term has become confused. Electric charge is a property of certain subatomic particles (e.g.' date=' electrons and protons) which couples to electromagnetic fields and causes attractive and repulsive forces between them.

 

Electric charge gives rise to one of the four fundamental forces of nature, and is a conserved property of matter that can be quantified. In this sense, the phrase "quantity of electricity" is used interchangeably with the phrases "charge of electricity" and "quantity of charge." There are two types of electricity or charge: we call one kind of electricity positive and the other negative. Through experimentation, we find that like-charged objects repel and opposite-charged objects attract one another. The magnitude of the force of attraction or repulsion is given by Coulomb's law. Some electrical effects are discussed under electrical phenomenon and electromagnetism.[/quote']

 

Are they the same? Not any more than a tree is the same as a forrest. Electricity is a kind of magnetism (as magnetism has to do with attractive forces, and Electricity is very specific about electrons and protons), but magnetism is not electricity.

 

Hope I helped, and hope someone can point out where I might be wrong.

[5614]

the change of the 'flow' of direction from Neg to Pos in the science books of old- it now seems to be Pos to Neg

They used to believe that electrical current flowed from positive to negative, however now we know that electrons move from negative to positive. At schools they are teaching that current moves from + -> - but that electrons move from - -> +

 

Is Magnetisuim (sorry about the speeling , the same as Electricity, as in static electricity, North-South / Pos-Neg?

Not really.

 

A static charge is when a thing (technnical here!) builds up a charge, so it will have more or less electrons than it is supposed to giving it an overal charge. So if it gains electrons then it will become negatively charged.

 

Magnetism can be from 1 of 2 causes. The first is the movement of electrons, so a current carrying wire will have a magnetic field. The other is a permament magnet, this is do with the unpaired electron spin.

 

So you can see they are both about electrons, but static = + or - electrons, whereas magnetism = moving/special properties of electrons.

[CPL.Luke]

Magnetism can be from 1 of 2 causes. The first is the movement of electrons, so a current carrying wire will have a magnetic field. The other is a permament magnet, this is do with the unpaired electron spin.

 

there both from moving electrons

 

however technically magnetism is caused by any moving charge. Just don't see many moving protons.

[Locrian]

Upaired electron spin is not due to moving electrons!

[swansont]

Upaired electron spin is not due to moving electrons!

 

Yes, but it's due to angular momentum. The "I can't believe it's not spinning" intrinsic angular momentum.

[Obba]

Well,

Thanks for all those replies people.

I can't say I understood the Atom / Molecule explanation - only in that the size of an 'grape' atom is to small in relation to a Molecule - so in essence that was what i really to clear up. I accept that Atoms cannot just be 'sized/measured' without looking at the other surroundings.

 

With the Electricity flow, i found this link yesterday after reading some of your replies.

 

http://www.amasci.com/amateur/elecdir.html

 

This, for me anyway, is what i could understand. And also covers the magnetism issue.

 

Great to have these forums, and i hope to be able to have my tuppence input in some of the other topics - which i will say are a little above my knowledge - but it's great stuff to read about these things.

 

Regards,

Alan.

[DQW]

I can't say I understood the Atom / Molecule explanation - only in that the size of an 'grape' atom is to small in relation to a Molecule - so in essence that was what i really to clear up. I accept that Atoms cannot just be 'sized/measured' without looking at the other surroundings.

A molecule is just a bunch of atoms "stuck" to each other. An oxygen molecule (represented as O₂) has two atoms of oxygen, and so, is no more than twice as big as an O atom. On the other hand, there are some truly large molecules (like proteins) which are made up of hundreds or thousands of atoms, and hence are much (tens or hundreds of times) bigger than one of those atoms.

 

As for measuring the size of atoms, that has been done pretty well too.