Need help with Compact Fluorescent

Are you saying the only light in the bathroom is in the fan? It sounds like you really want a light over the vanity mirror. My advice is to have an electrician add one. YMMV in what the California energy code allows

The wattage of a fluorescent lamp is determined by the ballast which in your case is part of the fixture. If you find a higher wattage lamp that will fit (socket should be keyed making this difficult), it still won't be any brighter than the smaller lamp. What you need to do is install an additional light fixture.

Yes but ...

Didn't "they" come up with "energy saving" 4' flourescent tubes that replaced the more or less "standard" 40 watt tube and only consumed 34 watts?

How did they do that?

EMWTK

The gas fill and pressure were altered to reduce the voltage drop across the lamp. When run on the HX autotransformer ballasts used on 4' lamps in 120V land, this causes the lamp to run at a lower wattage. It also causes the ballast to run hotter, so most ballasts made after these lamps were introduced were made to accomodate that.

On that note, very few ballasts will actually run a 34 or 40W tube at full power, you're lucky to see 30W out of most of them.

OK.

But, but (again) ...

If we are talking about a "conventional" ballast which is just an inductor, with the low power lamp, the voltage drop across the tube would a slight higher than "normal" and the voltage drop across the ballast would be slightly "lower" and the current would be significantly lower. Of course (and this may be the source of my error) the tube isn't exactly a linear load. Anyway, it would seem that the ballast should run slightly cooler. What am I missing?

EMWTK

Well those 4' tubes have been around for a LONG time. They are almost as old as the "improved" tungsten bulb with insert gas fill.

To digress, the government made a mistake when it "encouraged" the replacement of the 40 watt tubes with 34 watt tubes. Those tubes don't look all that great (even with fancy, in the ceiling fixtures). Folks only used them in the first place because they put out a LOT of light for the buck. I wonder how many officer workers ended up getting desk lamps because the ceiling fixtures just weren't putting out enought light.

It's the other way around, a higher wattage fluorescent lamp has a higher voltage drop, the current is the same, this translates to more wattage. With a choke ballast, the higher voltage across the lamp causes a lower current, so the wattage drops.

In this case he's not that far off. The CFL in question is not the screw-in retrofit type, it's a 2 pin lamp, so it very likely has a conventional choke ballast. Most of the electronic CFL fixtures use a 4 pin lamp so they can supply cathode heat.

My experience with CFL fixtures is mostly commercial grade stuff, in which the rare 2 pin lamps still use a choke and have a glow starter embedded in the base, but the 4 pin types use electronic ballasts. Many of the more recent ballasts support dimming as well, in which case cathode voltage ramps up as arc current decreases. Both the screw-in retrofits and the 4 pin lamps are available either straight or curly, though I see a lot more of the easier to manufacture straight type for external ballasts, and the screw in type is more often curly to approximate the shape of an incandescent lamp.

Electrically, a CFL is not that different from a 4 foot linear tube. The current tends to be lower, fill pressure is different, and the voltage drop across the tube is higher, but not by as much as one might assume. They're also a bit less efficient being a small tube driven harder to produce so much light.