In a message dated 4/29/98 3:20:22 PM Eastern Daylight Time,
> 12v 2.2W lamps/light bulbs are commonly available in the UK.
Buying a 12 volt light bulb is like buying a 2 X 4! Just as a 2 X 4 is not
actually 2" X 4", a 12 volt light bulb may not be rated at 12 volts. 12 volts
is the nominal value, just as 12 volts is the nominal value for the voltage of
a car battery. In good conditiopn, a car battery will produce 12.6 volts. As
an example of light bulb ratings, take the very common 1157 bulb, used in
almost every American car (at least in the older American cars). It is a dual
filament bulb, one filament rated at 27 watts and the other filament rated at
8 watts. If you look up the manufacturers specifications, you will find that
the brighter filament is rated at 2.1 amps at 12.8 volts, while the other
filament is rated at 0.59 amps at 14 volts.
If you go to an auto parts store to buy one, if it says anything at all on the
package, it will say 12 volts. For 99.00% of applications, that is close
enough. If you really need to know how much current it draws, you will have
to get the spec sheet and find out at what voltage the 27 and the 8 watts were
rated at. Then you will need to know what voltage it will be seing n your
application, which is very hard to do, as the voltage in a car varies from as
low as 11+ volts to as high as 15 volts. In a car with a properly
functioning alternator, the voltage will be around 14 volts most of the time.
If you go to the manufacturers spec sheet, as the gentleman who raised the
question did, you may find the 12 volt, 2.2 watt bulb you have is actually
rated at 14 volts. Or 12.8. Or 16. Or whatever.
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74