Q, an odd choice to represent ‘charge’? Electronic Products Word of the Week

How does the letter Q stand for “charge” in electricity? The unit of measure for charge is the coulomb, named for the French physicist Charles-Augustin de Coulomb (1736 – 1806), and the coulomb is abbreviated C, but Q?  

A little background is required. “Charge” relates to the predominance of electrons (negative charge) or deficiency of electrons (positive charge). Before “electricity” meant simply the power that came from plugging an appliance into a wall socket, scientists studied “electricity” because that word is rooted in the phenomenon of attraction, from the Latin electrum and the Greek electron (both meaning “amber”) when the ancients studied the ability of fossilized tree resin, amber, to attract other substances. Today the word “electronics” has taken over that study of electrons, as pointed out by Merriam-Webster,  which says that that word refers to “a branch of physics that deals with the emission, behavior, and effects of electrons (as in electron tubes and transistors) and with electronic devices.”

One of the aspects of “electricity” was its “quantity.” To quote the website bartleby.com:

“Negative and positive electricity . Two opposite conditions of the electric state of bodies. At one time electricity was considered a fluid, as heat was thought to be caloric. Everybody was thought to have a certain quantity. If a body contained more than its normal quantity it was said to be positive, if less, it was said to be negative in this respect. Another theory was that there were two different electric fluids, which neutralized each other when they came in contact. Electricity is now supposed to be a mere condition, like heat and motion; but its energy is set in action by some molecular disturbance, such as friction, rupture, and chemical action. The old terms are still retained.”

This “predominance” or “deficiency” of electrons, the principle we know as “charge,” was also called the “quantity of electricity.” “E” referred to electrons, so “Q,” after the first word of that phrase, came to represent “charge.” Wikipedia notes that “the term ‘quantity of electricity’ was once common in scientific publications. It appears frequently in the writings of Franklin, Faraday, Maxwell, Millikan, and J. J. Thomson, and was even occasionally used by Einstein.” All these scientists studied charge, and today that word is used instead of “quantity of electricity,” but the Q remains.

The simplified formula for charge — in the real world, the calculation can get quite complex — is 

Q = I t

Where

Q is charge in coulombs (C)

I is current in amperes (A)

t is time in seconds (s)