Ø <-- What is this called? How and where is it used?
(In case the symbol doesn’t show up on all screens, it’s a circle with a diagonal line through it).
It denotes a zero. So you do not get it confused with an “O” usually when hand writing something. I do not know it’s proper name aside from ZERO.
I know it is used as a zero, but isn’t it more properly known as “Null”
as in a Null Set {Ø}
A cipher, used for zero when the numeral 0 might be confused with the letter O, and used to indicate a null set in mathematics.
Are there other uses? For instance, I’m pretty sure it’s a regular letter in some languages, like in Danish. Specifically, I’m looking for deeper “symbolic” meanings. Like you have the Greek symbol omega. It’s a letter, it’s a mathematical symbol (used in electronics?), but it also has a sort of literary association with “the end”.
It’s also a Danish and Norwegian vowel.
Oh you want symbolic meanings. Ok, well in electrical engineering, it is the symbol for “phase”, as in a 3Ø motor.
Isn’t it also the lower case Greek letter Phi?
As a mathematician I consider that symbol the Greek letter Phi (as cybersnark says), which is used to denote an empty set.
However I am unable to find confirmation in mathworld. It’s possible it’s two different symbols that look the same.
I also thought that in a zero the crossbar didn’t protrude beyond the circle. But I’m really not sure of this.
Ø and { } both represent the null set, the set with no elements. {Ø} is a set with one element, that element being the null set.
Well, as Group 47, Symbol 4, it has a number of meanings, listed at that link. It’s also one of the symbols for the International Phonetic Alphabet.
That symbol is also used on some encrypted two-way radio and telephony equipment to denote operation in encrypted mode.
“Not”
Nope. The symbol for phase is the Greek letter phi which is different from the nordic O used for the null set.
No.
Correct.
Phi has a vertical line.
Null (and assorted meanings) = Ø (and when appearing as lower case in Scandinavian languages, ø)
Phi = [symbol]F f[/symbol] (upper and lower case)
I think you’ll find the symbol Ø used far more frequently in the industry than phi. I worked for a company that made, among other things, three-phase transformers. There were invariably marked ØA, ØB and ØC on the terminals. This symbol was also used on customer-supplied drawings for three-phase units from places like Allied Signal, G.E.C. Marconi and Kearfott Guidance & Navigation, so it wasn’t a mere idiosyncracy of my company. I have the definitive work ona this topic, The Electrical Engineer’s Reference Book, but it’s packed away and I can’t look it up right now, but I’m pretty sure they use the symbol Ø for phase as well.
Arghh, thats right, thanks DrMatrix. I can hear my 8th grade algebra teacher right now: intoning (over and over), “One or the other but not both.” Mrs. Gill would undoubtably be very disapointed in me right now.
People may be using the wrong symbol but they call it phi. i have never heard phase called anything else. If they are using another symbol it means they are using the wrong symbol for phi. Or what did you call phase? Null? I don’t think so. It is the Greek letter phi. Except maybe some people don’t know how to write it correctly or maybe they are using the wrong symbol.
Well, I did an unscientific survey with Google:
3Ø power - 4920 hits.
3F power - 1890 hits.
It may be, as you say, the wrong symbol, but it’s a popular wrong symbol–more so even than the “correct” one. I’d even go so far as to say at this point Ø is the correct symbol by default, purism be damned.