In a message dated 4/21/98 4:55:46 AM Eastern Daylight Time,
james.carpenter@ukaea.org.uk writes:
> YOu need to work out the total amps used buy the bulbs, which is, 54W/12
> = 4.5 amp.
James,
Almost. I wish it were that simple. Remember, 12 volts is like a 2 X 4, it is
a "nominal" value. Sitting at idle with lights, radio and heater on, with an
anemic alternator, the voltage could go as low a 11+. At road speed, the
voltage would be over 14.
Knowing that the 12 volts is a nominal value, one would think the the wattage
rating would also be a nominal value, based on 12 volts. Not so! I contacted
the technical department at Sylvania once to find out what voltage they used
to determine the wattage rating. I though it would be fairly simple -- either
the nominal 12 volts, or the actual 14.6 as supplied by the alternator. Nay,
nay, not so! The only way you can know what voltage was used is to get the
spec sheets and see. Some are rated at 12 volts, some at 14, and some at 16,
with a smattering of other voltages thrown in for good measure. When I asked
the engineer at Sylvania what voltage was used, I was greeted with a long
moment of silence. She put me on hold while she asked her supervisor. They
said no one had ever asked that question before.
I guess the engineers at the car companies had the spec sheets and didn't need
to ask, and the rest of us just assumed 12 volts and didn't ask. She was nice
enough to send me a copy of their catalog, with these values listed, so if
anyone wants to know, I will be happy to look it up for you.
Forgive the nit-picking, but I found that interesting, and thought I would
share it with you. For most purposes, 12 volts and the rated wattage is close
enough.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74
|