Something that is good to know is that lamp numbers mean the size.
A "T-8" fluorescent lamp is a
Tubular lamp 1" in diameter.
T-5 is 5/8" in diameter.
The numbers represent 1/8s of an 1".
Why 1/8s of an 1"?
I do not know.
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An R-40 is an
Reflector lamp 5" in diameter. 40 / 8 = 5
An S-11 is a
Sign lamp 1 3/8" in diameter.
The lamps we are most familiar with are Type A lamps
A-19, A-21, A-23 are common sizes
An A-21 would be 2 5/8" in diameter
Some more info can be found on these links
Incandescent Lamps
http://www.grainger.com/Grainger/static.jsp?page=rc_incandbaslamp.html Fluorescent Lamps
http://www.grainger.com/Grainger/static.jsp?page=rc_flurobaslamps.html HID Lamps
http://www.grainger.com/Grainger/static.jsp?page=rc_hidbaslamps.html Oh yeah you asked about a PAR lamp
PAR = Parabolic Reflector lamp
PAR 38 is a typical outside flood light used for years and it is 4 6/8" or 4 3/4" if you reduce the fraction, in diameter.
Bob
[This message has been edited by iwire (edited 12-04-2004).]
