﻿VK5AJL - Mathematical Symbols MATHEMATICAL AND OTHER SYMBOLS
AS USED ON THIS SITE

Some symbols are used to represent finite values such as Ω for ohms eg. 12Ω and others are used to represent unknown quantities eg. R for resistance. Some letters might be confused with various values eg. "I" is traditionally used for Current but might be confused with Inductance (generally L) or Impedance (generally Z). The letters or symbols used on this site, are listed here to prevent any such confusion.

English letters including strangely written ones

 j √-1 or the square root of -1. This number has no meaning in the normal real numbers. There is no negative number with a real square root. This is why vector quantities containg a j component are called imaginary although complex is also often used and propably a better adjective. " i " is often used instead of " j ". Z ZC ZL Symbol used for impedance. For a capacitor, impedance is written as ZC while for an inductor as ZL. Impedance should not be confused with reactance. Impedance is a complex quantity with real and imaginary parts. For a capacitor, ZC = - j / ωC while for an inductor, ZL = j ω L.|ZL| = |XL| when Ø = Π/2 WHILE |ZC| = |XC| when Ø = -Π/2 AND Z=R when Ø = 0 (Ø is the phase angle between voltage and current.) Impedance is used for both single components or complex circuits ie -Π/2 < Ø < +Π/2 X XC XL Symbol for reactance. For an inductor XL = ωL and for a capacitor XC = - 1/(ωC). Capacitive reactance is given as a -ve number because the current leads the voltage by Π/2 radians although the equation is often just written as XC = 1/(ωC) as a short form of |XC| = 1/(ωC) Reactance is usually a value associated with a single component. It doesn't make sense to use reatance when the phase angle is not +Π/2 or -Π/2. R Used to represent an unknown quantity of resistance. (See also Ω above.) f Frequency in cycles per second measured in Hz. L Used to represent inductance usually of an unknown quantity. Inductance is measured in Henries in which case H, or more commonly mH or μH, is used to represent a specific value. C Used to represent capacitance usually of an unknown quantity. Capacitance is measured in Farads in which case C, or more commonly μF, nF or pF, is used to represent a specific value. I Used to represent an unknown value of current. Current is measured in amps. V Many use E, EM or EMF to express Electro Motive Force. I prefer to simply use V to eliminate confusion with Electro Magnetic eg EM radiation. This site therefore uses V for both unknown and known quantities of volts. W or P An unknown quantity of power is usually expressed as "P" while a known quantity using "W" for watts. I have developed the, probably bad habit, of using W for both. This site will use "W" most of the time but "P" if I remember. All text and images on this site are Copyright to John Langsford (vk5ajl).
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I think that's pretty fair, don't you?