I would like to know what charge actually IS. Not the 'flow of electrons' charge but the charge because of which protons and electrons attract. I want to know why these attract and what the difference is between them. Why do we put a positive on a proton and a negative on an electron? They are 'positive' and 'negative' but what is the difference?

# [Physics] the difference between poisitive and negative charge?

chargeconventionselectricityelectromagnetismterminology

#### Related Solutions

When physicists say that a particle has electric charge, they mean that it is either a source or sink for electric fields, and that such a particle experiences a force when an electric field is applied to them.

In a sense, a single pair of charged particles *are* a battery, if you arrange them correctly and can figure out how to get them to do useful work for you. It is the tendency for charged particles to move in an electric field that lets us extract work from them.

A typical electronic device uses moving electrons to generate magnetic fields (moving electrons cause currents, and currents generate magnetic fields) and these magnetic fields can move magnets, causing a motor to turn. What is happening at a fundamental level is that an electric field is being applied (via the potential across the battery) that is causing those electrons to move.

If I wanted a magnetic field to be generated, I could get one from a single pair of charges, say, two protons placed next to one another. The protons will repel (like charges repel) and fly away from each other. These moving protons create a current (moving charge) which creates a magnetic field.

Your author is right when he says that charges attract or repel other charges. To help connect it to more familiar concepts, consider this: The negative end of your battery terminal attracts electrons and the positive end repels them. (The signs of battery terminals are actually opposite the conventional usage of positive and negative when referring to elementary charges. As a physicist, I blame electrical engineers.) The repelled and attracted electrons start moving, and these moving electrons can be used to do work.

In quantum theory of elementary particles (in a sense of irreducible representation of Poincare group with mass $m$ and spin (helicity) $s$) if some operator $\hat{Q}$ of internal symmetry commutes (like electric charge charge) with Hamiltonian $\hat{H}$ of given field theory, there must be $$ [\hat{Q},\hat{\varphi}^{\dagger}_{A}(\mathbf p)] | \rangle = q_{A}\hat{\varphi}^{\dagger}_{A}(\mathbf p), \quad [\hat{Q},\hat{\varphi}_{A}(\mathbf p)] | \rangle = -q_{A}\hat{\varphi}_{A}(\mathbf p). $$ Here $\hat{\varphi}^{\dagger}(x)$ is a field which creates particles while $\hat{\varphi}(x)$ is a field which creates antiparticles.

So you can see two facts: the particle has charge which is equal to the charge of corresponding antiparticle with minus sign; the setting of sign of particle's charge is formal. We can set the positron charge as negative, the physics doesn't change.

Charge is only the measure of interaction. Let's see this on the simple example.

We know that there is interaction between two electrons which can't be described as gravitational (they are repelled). Also we know that proton and electron are attracted (this interaction also can't be described as gravitational because it's stronger than it). Then we know that this interaction force at the simplest case coinsides with $\frac{1}{r^{2}}$ law, and the measure of interaction is constant in time. We need to build the theory with these properties. The charge of given particle, as (for simplicity) the mass in case of gravitational interaction, says us about its taking part in interaction.

## Best Answer

I glanced through the proposed duplicates, and I want to put in the point of view of an experimentalist.

There exists an everyday word called "electricity." The root comes from the greek word for amber ηλεκτρον. Amber is a naturally found "stone", fossilized tree resin, and its property of attracting stuff was known from ancient times.

It is an

observational factthat some matter, when rubbed, displays attraction and repulsion. This is two states, and mathematically easily described by assigning a positive sign and a negative sign to the variables eventually used to measure the observed effects.That charge is carried by particles was found experimentally in the cathode ray tubes, and the assignment of the charges to particles follows the history of physics from then on. Consistency in assignments is important, but whether the electron was dubbed with a negative charge giving the proton a positive one is just a historical fluke.

These observations were organized into laws, which were unified in the electromagnetic theory so well modeled with the mathematics of Maxwell's equations. . The quantum mechanical framework of nature is consistent with the macroscopic observations and incorporates the effect in the mathematics.

I just want to stress that physics is about describing observations and data with mathematical models. To do that there are certain postulates, laws, principles that are assumed so that the mathematics fits the observations. The existence of two charges is one of the basic observational facts incorporated into the mathematical models of nature, the sign is arbitrary but consistent, and historically it is the electrons that are called negative.

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