In physics the term Quantity of Electricity refers to the quantity of electric charge. It is designated by the letter Q and is measured in terms of SI derived units called coulombs.
Historical Drift
The term Quantity of Electricity was once common in scientific publications. It appears frequently in the writings of Franklin, Faraday, Maxwell, Millikan, and JJ Thomson, and was even occasionally used by Einstein.
However, over the last hundred years the term "Electricity" has been used by electric utility companies and the general public in a non-scientific way. Today the vast majority of publications no longer refer to Electricity as meaning electric charge. Instead they speak of Electricity as electromagnetic energy. Some authors even use "electricity" to mean electric current (amperes), energy flow (watts), electrical potential (volts), or electric force.
It is probably for this reason that Quantity of Electricity has fallen into disfavor among scientists. Quantity of Electricity is now regarded as an archaic usage, and it has slowly been replaced by the terms Charge of Electricity, then Quantity of Electric Charge, and today simply Charge. Since the term Electricity has increasingly become corrupted by contradictions and unscientific definitions, instead we use the term Charge to remove any possible confusion.
Conceptual Problems
However, fixing problems by replacing the term "Electricity" with "Charge" in itself causes problems. Older scientific papers still exist, and their authors discuss Quantities of Electricity and Flows of Electricity (meaning charge and current respectively.) Those historical authors assume that their readers are conscious of only one definition: the term Electricity means Charge and nothing else. While reading physics papers from periods prior to 1930 (approx.), the student should make a continuous effort to remain aware of this issue. If historical physicists discuss quantities of "electricity" meaning "electric charge," yet the modern reader assumes they're speaking of electrical energy, the writings of those physicists will be quite difficult to understand.
Another problem arises because the population of physicists abandoned the term "Electricity" without much public discussion and perhaps without much awareness on the part of the physics community. By silently altering the common usage of terms, the community produced an immense confusion on the part of the public. Whereas in the past the question "What is Electricity" was more or less easily answered, today the question itself has become meaningless. Is electricity a form of energy? Is electricity the same as electric charge? Is electricity nothing but a class of phenomena, akin to concepts such as "weather" or "politics?" Should we measure the quantity of electricity in coulombs, or should we instead use amperes, joules, or watts, or volts? Physics texts and references supply no solid answer, since physicists have gradually and silently abandoned Electricity as a scientific term.
And yet Quantity of Electricity still persists in its original definition in many contemporary references. For example, in the modern SI units of physics, the Coulomb is defined both as the unit of electric charge and also the unit Quantity of Electricity. The Merriam-Webster dictionary, in definition 1a, defines electricity as charge. Another example: until the 1970s, the CRC Handbook of Chemistry and Physics used the term "Quantity of Electricity" in place of "Electric charge" in most of its definitions of physics terms. And chemistry students will be familiar with Faraday's discovery that a unit Quantity of Electricity, when passed through an electrolysis cell, liberates a certain number of atoms of metal or gas.
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Last updated: 08-17-2005 02:07:55
