[modeleng] Re: Low voltage lighting

Hi Dave

On the face of it, you'd think that as Watts = Volts x Amps, any number of 
combinations of voltage and current would give the same brightness in a 
bulb.  However the Wattage quoted is only valid for the rated voltage.  This 
is because the resistance of the filament remains constant.  Thus if you 
halve the voltage, you will halve the current (Ohm's law).  The wattage will 
then be 1/2 x 1/2 = 1/4 of what it was before, so no wonder your bulb was 
dim!

Still looking for 3-pin bulbs!

Regards
Ron

----- Original Message ----- 
From: "David Everett" <deverett2003@xxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Saturday, July 30, 2005 4:05 AM
Subject: [modeleng] Re: Low voltage lighting


> Hi Ron
>
> I have a story to tell about lo volt lighting, which will explain my 
> flippant remark:
>
> Last year I bought a lathe with 3-phase electrics and included was a 
> Lo-Volt light run through a
> 440-50 volt transformer.  I am running the lathe through a 1 - 3 phase 
> inverter, so the lighting
> transformer isn't connected.  In my electrical wisdom I bought a 25 volt 
> bulb (standard 2 pin BC)
> from The Electric Light Bulb Company.  My thinking was that 220v = 1/2 x 
> 440v so that a 25 volt
> bulb run off 220volts should be the same as a 50 volt bulb run through 440 
> volts.  Not so.  The
> bulb glowed dimmer than a TochH lamp!
>
> So I went out and bought a Halogen machine lamp instead!  Instant cure.
>
> Anyone need a 440v - 50v Lo-volt Machine light?!
>
> Regards
>
> Dave
>



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