Energy

[Marm]

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?

[Xei]

Energy is the ability to 'do work'. Doing work means applying a force over a distance. If you lift a brick which weighs 1 Newton by 1 metre it gains 1 Joule of potential energy.

[Original Poster]

What is an electromagnetic field?

[Xei]

It's a kind of combination of electric fields and magnetic fields, which describe vectors at every point in space, characterising the electromagnetic forces due in general to moving charges.

[Original Poster]

Can you give me an example of how this works?

[Xei]

Sure, imagine a point charge of strength Q at the origin. This creates an electric field defined by vectors at every point other than the origin of length Q/kr^2 where r is the distance from the origin, pointing outwards from the origin. These describe the force on a unit point charge. I hope you learned a lot today.

[Original Poster]

Not yet. Please use laymen's terms.

[Xei]

I was using layman's terms. You can look all of them on Wikipedia, they are simple concepts. Charge is just a numerical property of objects. Q is such a number. A vector is a length with a direction, so in other words an arrow. Force is a type of vector. When a force is applied to an object, that object accelerates in the direction of the vector with acceleration proportional to the length of the vector and inversely proportional to the mass of the object. So what we have is a stationary particle with a charge creating virtual arrows at every point in space (this is the electric field). The arrows describe how a particle of unit mass and charge will accelerate. They point away from the stationary particle and their length decreases the further away they are, and they are bigger if the charge is bigger.

[Marm]

Energy is the ability to 'do work'. How do you relate work done to other forms of energy such as electric/nuclear/magnetic energy?

[Wayfaerer]

The electromagnetic and nuclear forces applied over a distance?

[Wayfaerer]

Energy is kind of hard to pin down. The question of "what is it?" is especially interesting because of the fact that it's quantized. Pauli's Exclusion principle shows these discrete levels have some real, awesome, and diverse consequences.

[Original Poster]

Electric fields are created by differences in voltage: the higher the voltage, the stronger will be the resultant field. Magnetic fields are created when electric current flows: the greater the current, the stronger the magnetic field. An electric field will exist even when there is no current flowing. If current does flow, the strength of the magnetic field will vary with power consumption but the electric field strength will be constant. A simple analogy should help to illustrate the concept: Tie a long rope to a door handle and keep hold of the free end. Moving it up and then down slowly will generate a single big wave; more rapid motion will generate a whole series of small waves. The length of the rope remains constant, therefore, the more waves you generate (higher frequency) the smaller will be the distance between them (shorter wavelength). Plugging a wire into an outlet creates electric fields in the air surrounding the appliance. The higher the voltage the stronger the field produced. Since the voltage can exist even when no current is flowing, the appliance does not have to be turned on for an electric field to exist in the room surrounding it. Magnetic fields are created only when the electric current flows. Magnetic fields and electric fields then exist together in the room environment. The greater the current the stronger the magnetic field. High voltages are used for the transmission and distribution of electricity whereas relatively low voltages are used in the home. The voltages used by power transmission equipment vary little from day to day, currents through a transmission line vary with power consumption. I looked it up here. WHO | What are electromagnetic fields?

[Xei]

Erm... good for you bro.

[Original Poster]

I don't think you understand half the shit you know.

[Arra]

For some reason I find this thread and Xei's reactions, and people's reactions to his posts in general, fucking hilarious. As for energy, the thing is, it isn't a 'thing'. There are no energy particles, as is often imagined. The reality is that some matter accelerates, some objects have potential energy, etc. When something bumps into something else, that other thing accelerates, then decelerates, and heat and sound result. It's all quantifiable, so that the initial energy equals the sum of the final energies, so it's easy to put the 'energy' label on it, as though it's a thing. Even the fact that energy is 'transferred' is kind of an illusion, but it mathematically works out that way, so it's easy to think of it like that. I could be wrong though. Correct me if I am. I've told only one person my viewpoint on this before and he disagreed.

[cmind]

For some reason I find this thread and Xei's reactions, and people's reactions to his posts in general, fucking hilarious. We all get a laugh from the giant small boner Xei gets every time he has the opportunity to demonstrate his knowledge.

[Arra]

We all get a laugh from the giant small boner Xei gets every time he has the opportunity to demonstrate his knowledge. I didn't see it in this thread. He acts pretty modest about it actually. Of course there's going to be some pride... but he isn't as bad as others.

[Xei]

I don't think you understand half the shit you know. I don't think you know anything. What is this comment even based on rofl, you repeatedly asked random questions and I repeatedly answered them clearly.

[Original Poster]

Clearly your idea of clearly is a matter of opinion. I got the impression that you were listing qualities and giving book definitions but were unable to describe what an EM field actually is, in reality. This is a classic activity by people that don't understand what they've learned. You spent too much time writing down answers and not enough time considering what they mean.

[Wayfaerer]

You must be talking about the whole scientific community then, because that's the definition of a field.

[Original Poster]

>.> I did not say Xei was lying. I said it's revealing that Xei has no clue what he's talking about when he can only explain something by reciting the definition.

[Wayfaerer]

How else would you explain something?

[Original Poster]

I'd use terminology that more effectively conveys the idea rather than define it, such as an example.

[Spartiate]

Can you give me an example of how this works? Sure, imagine a point charge of strength Q at the origin. This creates an electric field defined by vectors at every point other than the origin of length Q/kr^2 where r is the distance from the origin, pointing outwards from the origin. These describe the force on a unit point charge. I hope you learned a lot today. .

[Original Poster]

Right. That part made no sense to me. That's why I had to look it up on my own and ended up posting the link to what I looked up in order to help other people who also couldn't comprehend what an EM field was or how it works based on that definition. I don't see how anyone can read that and take meaning from it unless they've already taken a lecture. I find Xei's description vague at best.