Even the terms "positive" and"negative" arearbitrary, but well-entrenched historical labels. Theproton has1836 times the mass of the electron, but exactly the same sizecharge, onlypositive rather than negative. The most importantopening idea,electrically, is that they have a property called "charge" which isthe samesize, but opposite in polarity for the proton and electron. No significanceshould be attached to the circles representing the proton and electron, inthe senseof implying a relative size, or even that they are hard sphereobjects,although that's a useful first construct.
In introducing one of the fundamental properties of matter, it is perhaps appropriate to point out that we use simplified sketches and constructs to introduceconcepts, and there is inevitably much more to the story. The rate of flow of electric charge is called electric current and is measured in Amperes. Two charges of one Coulombeach separated by a meter would repel each other with a force of about a million tons! One Coulomb of charge is the charge which would flow through a 120 watt lightbulb (120 volts AC) in one second. The influence of charges is characterized in terms of the forces between them ( Coulomb's law) and the electric field and voltage produced by them. Charge is quantized as a multiple of the electron or proton charge: Ordinary matter is made up of atoms which have positively charged nuclei and negatively charged electrons surrounding them. The unit of electric charge is the Coulomb (abbreviated C). HyperPhysics***** Electricity and Magnetism The standard abbreviations for the units are 1A = 1C/s.
In most DC electric circuits, it can be assumed that the resistance to current flow is a constant so that the current in the circuit is related to voltage and resistance by Ohm's law. Electric current is the rate of charge flow past a given point in an electric circuit, measured in Coulombs/second which is named Amperes.
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