Why?Matterwave said:The magnetic field is as necessary to explain the motion of charges just as much as the electric field is.
k9b4 said:Why?
Does a magnetic field cause charged particles to move?Matterwave said:The electric field only gives you the forces between charges which are static. Once the charges start to move, they will see magnetic fields come into play and require both the electric field and magnetic field to figure out their motion.
This is a pretty broad field, so maybe look here first: http://en.wikipedia.org/wiki/Magnetic_field
k9b4 said:Does a magnetic field cause charged particles to move?
Why does a magnetic field only affect charged particles when the magnetic field is moving? A static electric field created by a charged particle will attract or repel other charged particles.Matterwave said:A static magnetic field won't cause a static charge to move, but it will change its direction of motion once it does start moving.
The full force law considering both electric and magnetic fields is the Lorentz force law:
$$\vec{F}=q(\vec{E}+\vec{v}\times\vec{B})$$
k9b4 said:Does a magnetic field cause charged particles to move?
k9b4 said:Why does a magnetic field only affect charged particles when the magnetic field is moving? A static electric field created by a charged particle will attract or repel other charged particles.
This is just a little nitpick, but the magnetic field only affects charged particles when the charged particles are moving. The magnetic field itself doesn't have a velocity, although changes in the electromagnetic field do.k9b4 said:Why does a magnetic field only affect charged particles when the magnetic field is moving?
But I like to think about what is actually there. A field is not actually there. An electron however, has a mass and exists in reality.Drakkith said:Also, you need to understand that the entire concept of a "field" is a mathematical and conceptual way to make sense of how particles interact. Fields are used extensively in physics because they offer what is probably the simplest way of understanding much of the fundamental interactions of nature. They are so useful that entire theories have been developed to describe even particles in terms of an underlying field. (See the various Quantum Field Theories)
Trying to understand how particles interact without understanding the field that describes their interaction is not going to get you anywhere.
Just because my questions might be difficult to answer, doesn't mean that they don't have an answer.Mark44 said:k9b4, you've asked a lot of "why" questions. Here's a video of Richard Feynman on magnetism and "why" questions and how difficult they are - http://www.bing.com/videos/search?q=Feynman Magnets&Form=VQFRVP#view=detail&mid=EBC66564088F7695161DEBC66564088F7695161D.
Feynman's point is that the person asking "why" might not have enough background knowledge to understand the answer.k9b4 said:Just because my questions might be difficult to answer, doesn't mean that they don't have an answer.
But I'm asking for an intuitive answer, not a mathematical one. "I don't know" is a perfectly acceptable answer.Mark44 said:Feynman's point is that the person asking "why" might not have enough background knowledge to understand the answer.
k9b4 said:But I like to think about what is actually there. A field is not actually there. An electron however, has a mass and exists in reality.
k9b4 said:But I'm asking for an intuitive answer, not a mathematical one. "I don't know" is a perfectly acceptable answer.
A field doesn't exist in the sense that it has no mass. I am using the word "exist" to mean "has mass". Therefore, something with no mass does not exist. Energy is another thing which does not exist according to this definition. I agree that both energy and fields are useful concepts to help understand how things work, but both do not possesses mass and are "not actually there".Drakkith said:How do you know the field isn't actually there? Keep in mind that a particle is no less mathematical or conceptual than a field is. And if the field isn't there, what happens to the energy lost from radiating particles before the radiation is absorbed by another particle? Is that energy simply gone? If the field doesn't exist, then why do field theories have such success over purely particle theories?
A field allows us to answer questions like this by treating the field as an actual entity and not just clever math. (of course one could argue that all math is "clever math" if it enables us to accurately describe reality, whether or not that math is for particles or fields)
Drakkith said:There aren't always intuitive answers. Sometimes reality simply doesn't match up with our intuition. The key is to realize that intuition isn't something that is set in stone, but is something that can be molded as you learn more. Many things that don't make sense to you now will probably be absolutely obvious in the future.
Drakkith said:How do you know the field isn't actually there? Keep in mind that a particle is no less mathematical or conceptual than a field is. And if the field isn't there, what happens to the energy lost from radiating particles before the radiation is absorbed by another particle? Is that energy simply gone? If the field doesn't exist, then why do field theories have such success over purely particle theories?
A field allows us to answer questions like this by treating the field as an actual entity and not just clever math. (of course one could argue that all math is "clever math" if it enables us to accurately describe reality, whether or not that math is for particles or fields)
Your definition of existence is oversimplistic. By your definition, light and other electromagnetic radiation don't exist (because photons don't have mass) nor do neutrinos. If these things don't exist, how do you account for the fact that we can detect light with our eyes, and we can detect neutrinos by their (rare) interactions with other atoms.k9b4 said:A field doesn't exist in the sense that it has no mass. I am using the word "exist" to mean "has mass". Therefore, something with no mass does not exist. Energy is another thing which does not exist according to this definition. I agree that both energy and fields are useful concepts to help understand how things work, but both do not possesses mass and are "not actually there".
Drakkith said:There aren't always intuitive answers. Sometimes reality simply doesn't match up with our intuition. The key is to realize that intuition isn't something that is set in stone, but is something that can be molded as you learn more. Many things that don't make sense to you now will probably be absolutely obvious in the future.
I disagree. Just because no one has yet come up with an answer that a layman could understand doesn't mean that a concept isn't well understood.k9b4 said:I don't believe there aren't always intuitive answers. I believe that lack of an intuitive answer simply means that no one fully understands what's going on yet.
Yes exactly. Electromagnetic waves do not exist because electromagnetic waves are electromagnetic fields, which do not exist. Our seeing of light can be explained simply by oscillating charges causing electrons in our eyes to oscillate which sends electric signals to our brains which we perceive as light. No electromagnetic fields/waves need come into the picture.Mark44 said:Your definition of existence is oversimplistic. By your definition, light and other electromagnetic radiation don't exist (because photons don't have mass) nor do neutrinos. If these things don't exist, how do you account for the fact that we can detect light with our eyes, and we can detect neutrinos by their (rare) interactions with other atoms.
Yes I watched the Feynman video. He was saying that It's difficult to communicate difficult concepts to laymen because they lack background knowledge required right? I was under the impression that the background knowledge he was referring to was purely mathematical.Mark44 said:I disagree. Just because no one has yet come up with an answer that a layman could understand doesn't mean that a concept isn't well understood.
Did you watch the Feynman video? It was directly related to the questions you're asking.
k9b4 said:Electromagnetic waves do not exist because electromagnetic waves are electromagnetic fields, which do not exist. Our seeing of light can be explained simply by oscillating charges causing electrons in our eyes to oscillate which sends electric signals to our brains which we perceive as light. No electromagnetic fields/waves need come into the picture.