Thread: Energy

None of the stuff you quoted defined or explained what an EM field is, which was the question you asked me.

You asked for an example and I gave you one. Did anybody else have difficulty with it? What was confusing about it? It's just basic human concepts like space and length.

I suppose this is just where you and I differ. I don't think you understand something unless you can explain it to your grandmother.

Omnis is insufferable, but he's right about that "example". Xei used terminology that no layman would know, like "point charge" or "the origin". Ask 10 people on the street what these physics terms mean and I guarantee you 9 of them won't know.

Originally Posted by Omnis Dei

I suppose this is just where you and I differ. I don't think you understand something unless you can explain it to your grandmother.

I understood Xei's explanation, and I disagree with you. Being very articulate does not equal intelligence.

Originally Posted by Omnis Dei

I suppose this is just where you and I differ. I don't think you understand something unless you can explain it to your grandmother.

You still didn't explain what you didn't understand about it.

If you actually cared you would have asked me what any terms you didn't get meant. It's not my fault that I can't read your mind and tell what you're ignorant about. Nobody can explain something to their grandmother if their grandmother just sits there and stares at them.

Originally Posted by cmind

Omnis is insufferable, but he's right about that "example". Xei used terminology that no layman would know, like "point charge" or "the origin". Ask 10 people on the street what these physics terms mean and I guarantee you 9 of them won't know.

That is true. But, an explanation in laymen's terms is usually

Originally Posted by Omnis Dei

vague at best.

Not the other way around.
Xei's explanation was accurate, it just seems vague because you may not understand what some of the terms meant.

But there's very few people that can accurately explain things in laymen's terms. The only one I know of is Carl Sagan.

I could be mistaken because I do not know a lot about magnets but I believe magnetic fields is caused by electrons gathering in one area. So basically if you have a magnet the electrons move to one side of the object causing that side to be negatively charged, while the other side is positively charged due to lack of electron.

Originally Posted by Alric

I could be mistaken because I do not know a lot about magnets but I believe magnetic fields is caused by electrons gathering in one area. So basically if you have a magnet the electrons move to one side of the object causing that side to be negatively charged, while the other side is positively charged due to lack of electron.

Hmm, something seems fishy about this explanation...

What is fishy about it? There are magnets that have natural magnetic field because of the shape of how the atoms connect and the position of the electrons. Then there are magnets fields you create by passing electricity(electrons) through the metal. In that case its the flow of electrons that creates the field.

Originally Posted by Xei

You still didn't explain what you didn't understand about it.

If you actually cared you would have asked me what any terms you didn't get meant. It's not my fault that I can't read your mind and tell what you're ignorant about. Nobody can explain something to their grandmother if their grandmother just sits there and stares at them.

You're right, I gave up on you the instant you said "I hope you learned a lot today."

I guess the way you treat the person you are talking to is also important.

Originally Posted by Omnis Dei

You're right, I gave up on you the instant you said "I hope you learned a lot today."

I guess the way you treat the person you are talking to is also important.

You are a horrible poster, please leave.

Originally Posted by Alric

What is fishy about it? There are magnets that have natural magnetic field because of the shape of how the atoms connect and the position of the electrons. Then there are magnets fields you create by passing electricity(electrons) through the metal. In that case its the flow of electrons that creates the field.

I don't think it's 'fishy' as such, more just, incorrect. I think what you described is actually essentially something that would cause an electric field. It has the classic shape that you are thinking of but would apply to charges, not magnets. But it couldn't stay in that form anyway, electrons are free to move through a metal, and so wouldn't cluster towards one end for very long before restoring equilibrium.

Magnetism is generally caused by moving charge. Stationary magnets work because of trippy quantum shit to do with electrons (I think spin) which I make no pretensions towards understanding.

Originally Posted by Marvo

You are a horrible poster, please leave.

Why? Because I have trouble learning from people who can't explain anything without their tongue in their cheek?

Originally Posted by Xei

Magnetism is generally caused by moving charge. Stationary magnets work because of trippy quantum shit to do with electrons (I think spin) which I make no pretensions towards understanding.

Individual electrons have spin, which produces a small magnetic field. In ferromagnetic materials that have been exposed to an external magnetic field (like the field of the Earth), Pauli Exclusion essentially makes it energetically favourable for the electrons to line up their spins, thus setting up a uniform internally-generated magnetic field. The reason this happens in some metals and not others has to do with the exact number of electrons in each orbital, which is determined by atomic number. Other metals, called diamagnets, line up their electron spins to try to cancel out any external magnetic field.

I won't get into magnetic domains because that would take too long to explain.

I do believe they are similar to electric fields though. In the case of natural magnets, the atoms are balanced but its the shape of the atoms that causes the electrons to go to one end. The electrons don't separate from the atoms though, and are still held together, but are pushed in that one direction.

I went ahead and looked up the differences between magnetic fields and electric fields though, since I am not entirely sure. From my understanding from what I read about it, electric fields are areas around charged particles, and magnetic fields is the area around moving charges.

So in the example I gave of creating a magnetic by running electricity through an object, it would create both an electric and magnetic field. In the case of a permanent magnet there is no overall charge but the electrons are still moving around. Which seems to fit with what I said.

That does make sense, and I do know about electron spin or at least the basics of it. I do plan to take physics classes in the future, but so far what I know about spin come from chemistry.

When it comes to electromagnets though, do the electrons still spin in the same way? Or does it just function similar to spin, because the current is traveling in a circle in one direction?

Originally Posted by Alric

When it comes to electromagnets though, do the electrons still spin in the same way? Or does it just function similar to spin, because the current is traveling in a circle in one direction?

In an electromagnet it's the current that produces the magnetic field. The electron spins are most likely completely random.

If you want to understand more about diamagnetism and paramagnetism, look up Molecular Orbital Theory. Interestingly it makes some predictions that you wouldn't otherwise expect, such as the ground state of O2 being paramagnetic (and a higher energy diamagnetic state that has different chemistry). It also explains stuff like why most transition metal compounds tend to be coloured. (Well strictly speaking it doesn't exactly, but Crystal Field Theory shares a lot in common with MO)

All very interesting stuff.

Edit: The wikipedia article on Magnetochemistry explains quite a few things as well.

Kinetic energy = (1/2)(mass)(velocity^2)
Gravitational Potential Energy = (mass)(acceleration due to gravity)(height)
Spring Potential Energy = (1/2)(spring constant)(distance from equilibrium)^2

Originally Posted by Hercuflea

Kinetic energy = (1/2)(mass)(velocity^2)
Gravitational Potential Energy = (mass)(acceleration due to gravity)(height)
Spring Potential Energy = (1/2)(spring constant)(distance from equilibrium)^2

Leaving out the fact that this is a huge necro-post, formula such as these do not explain what energy is, they simply allow us to convert from one kind of energy to another.

And because I'm in that kind of a mood today, they aren't actually accurate.
Kinetic energy is given by Ek = mγc^2 - mc^2 due to relativity (Though the formula works well enough for speeds < ~0.1c), where m is the mass of the object, c is the speed of light in vacuum and γ is the square root of 1/(1-v^2/c^2), where v is the speed the object is traveling
The acceleration due to gravity isn't actually constant, but works out to G(m1/r^2), where G is a constant ~6.67384 * 10^-11, m1 is the mass of the earth and r the distantance from the earth's center of mass.
And Hooks law in an approximation for the non-deformative range of a spring.

Sorry, man. I'm just in Physics 1!

Dont rape me.


(Didnt realize that thread was old, was on first page)

Originally Posted by Hercuflea

Sorry, man. I'm just in Physics 1!

(Didnt realize that thread was old, was on first page)

After hours of working on evil quantum mechanics, I just wanted to spread the pain. And it's not like I've ever had cause to use the formula I posted rather than those you did. As I said, was in that kind of a mood.

And yeah, this subforum doesn't see much use.

Originally Posted by LightofHeaven

We use the word 'energy' a lot in all fields of science, but what is it? How do we define it? I find that it is actually quite difficult to pin down a specific definition, because it can come in many difference guises.
So, what is energy?

Energy is the capacity of a system to perform work