Thread: Charge

We all know like charges repel and opposite ones attract, we also know electrons are negatively charged particle and protons are positively charged; which is contributed bu quarks with 1/3 of the charge, but what is driving me crazy is what exactly is charge and what does negative charge means?

Somebody please help me on this?

I can't answer what charge is, but I can tell you that positive and negative are just arbitrary terms. There's no reason to call it one way or the other, but we have to pick one, and this is what we ended up with.

but again what is it in a charge that attarcts the ones which possess opposite of them and repels the one that possesses the like ones. Similarly what exactly is magnetism, till now I have learnt that either moving charged particle, or angular and spin moment of electron generated magnetism. But what exactly is magnetism, what is in it that like poles repel and opposite attract? Does any theory in physics elaborate about them apart from their nature? Do quantum theory help?

That is explained by QM, but I don't know enough details to give you a good answer.

Originally Posted by sarath_2012

We all know like charges repel and opposite ones attract, we also know electrons are negatively charged particle and protons are positively charged; which is contributed bu quarks with 1/3 of the charge, but what is driving me crazy is what exactly is charge and what does negative charge means?

Somebody please help me on this?

A couple of things.

1. Electrons seem to be elementary particles and are not composed of quarks.

2. Protons and neutrons are composed of quarks. The theory that explains this is called quantu chromodynamics and it is considerabley more elaborate and difficult than the theory that explains electromagnetic phenomena at the quantum level, quantum electrodynamics, which is itself fairly complex.

3. Electric charge is a quantum property. The negativity of electron charge is a convention. It is completely arbitrary. It could just as easily have been called positive in which case the positron would have negative charge. But it is the other way around -- thank Ben Franklin for that.

4. Quarks also carry a color charge that describes the strong force, which is part of quantum chromodynamics.

5. Electric charge is nothing more than way of expressing the electrostatic force and saying protons attract electrons and repel protons and the electrons also repel electrons. It is not explainable in terms of something else

How is an electron treated to figure its orbital's shape in quantum mechanics? I mean what does it mean 'wave-like behavior' of an electron?

Originally Posted by sarath_2012

How is an electron treated to figure its orbital's shape in quantum mechanics? I mean what does it mean 'wave-like behavior' of an electron?

The position of an electron is not defined precisely in quantum mechanics, but only in terms of the probability that, if a measurement is taken, it will be found in a given region. The probability density is determined by the Schrodinger equation, and that equation is a wave equation.

To go much further, you need to read a good textbook on quantum mechanics.

Why do we have only x,y.z plane? When talking about p-orbital's shape and its orientation in x,y,z plane, how can we say it as a dumbbell shape when the position of an electron is not certain and still why do we show it only in x,y,z plane. When going by the principle and infinite directions of orientation all the orbital should essentially acquire a spherical shape. Please enlighten me here.

Originally Posted by sarath_2012

Why do we have only x,y.z plane? When talking about p-orbital's shape and its orientation in x,y,z plane, how can we say it as a dumbbell shape when the position of an electron is not certain and still why do we show it only in x,y,z plane. When going by the principle and infinite directions of orientation all the orbital should essentially acquire a spherical shape. Please enlighten me here.

Th electron's position is uncertain within that dumbbell shape. Three planes are all you need to describe any 3-D shape.

Originally Posted by sarath_2012

but what is driving me crazy is what exactly is charge and what does negative charge means?

"positive" and "negative" are just an arbitrary way to describe the fact that they're opposites. A "negative" charge isn't negative in the sense that you would ordinarily imagine, like as an "absence" or a "void".

A lot of people who work with electricity think it would have been easier to understand electrical theory if we switched the names. The electrons in a wire actually flow from the negatively charged end to the positively charged end.

http://www.rare-earth-magnets.com/t-...tron-flow.aspx

Originally Posted by DrRocket

Originally Posted by sarath_2012

We all know like charges repel and opposite ones attract, we also know electrons are negatively charged particle and protons are positively charged; which is contributed bu quarks with 1/3 of the charge, but what is driving me crazy is what exactly is charge and what does negative charge means?

Somebody please help me on this?

A couple of things.

1. Electrons seem to be elementary particles and are not composed of quarks.

2. Protons and neutrons are composed of quarks. The theory that explains this is called quantu chromodynamics and it is considerabley more elaborate and difficult than the theory that explains electromagnetic phenomena at the quantum level, quantum electrodynamics, which is itself fairly complex.

3. Electric charge is a quantum property. The negativity of electron charge is a convention. It is completely arbitrary. It could just as easily have been called positive in which case the positron would have negative charge. But it is the other way around -- thank Ben Franklin for that.

4. Quarks also carry a color charge that describes the strong force, which is part of quantum chromodynamics.

5. Electric charge is nothing more than way of expressing the electrostatic force and saying protons attract electrons and repel protons and the electrons also repel electrons. It is not explainable in terms of something else

could u elaborate what do u mean by electric charge is a quantum property..

because i thought charge was just a measure of how strong to create a electrostatic forces.. am not defining charge but just giving my opinion..

anyways i also thought what is it that we call charge as charge is..

Just as a mass creates a gravitational field, which general relativity describes as a curvature of space/time, a charge creates an electromagnetic field which acts on other charged particles by accelerating them positively or negatively. This away or towards convention gave rise to positive and negative charge since up to 100 yrs ago only electrons moved.

As you approach quantum level size all aspects of reality take on a wave particle duality, so that electrons, and other particles, have an associated wavelength (see deBroglie) and can be treated by wave mechanics. As for the dumbell shaped electron probability orbits. they are more easily described in spherical polar co-ordinates, not cartesian co-ordinates (x-y-z). As a matter of fact, to solve the 2nd order partial differential equation describing the Hydrogen atom, unless you convert to spherical polar co-ordinates, you cannot use separation of variable along with boundary cosiderations to simplify and get a solution.

"What is charge"--this has to be my all-time favorite question on this forum because the mathematical subject matter is so close to my heart.

Unfortunately, the answer is highly non-trivial, so I'll attempt to give a low-tech answer, and if people are truly interested, maybe I'll follow up with more detail.

The word "charge" in physics actually has a broader meaning than the use you've probably encountered up to this point. Basically "charge" refers to measureable quantities that are conserved. Energy, momentum, and electro-static charge are actually all examples of conserved "charges".

In physics, there is a duality between symmetries and conserved charges. Basically, for every continuous symmetry of a physical system, you get a corresponding conserved charge. Some examples:

Time-translational symmetry---->Conservation of Energy
Space translational symmetry--->Conservation of Momentum
U(1) symmetry-------------------->Conservation of Electric Charge

You're probably familiar with the first two symmetries, but the third one probably throws you off. It's actually not hard to explain though. It essentially means this:

If you go and look at the equations of motion for an electron (in quantum field theory), then the equations don't change if you multiply all the electron-related terms by for any angle . So the field equations for an electron exhibit a kind of rotational symmetry. It is this symmetry which gives rise to this conserved quantity whose properties we recognize as electric charge.